5,788,814 issued 04-Aug-98 to Sun, CHUCKS AND METHODS FOR POSITIONING MULTIPLE OBJECTS ONA SUBSTRATE ; Pat. No. 5,753,302 issued 19-May-98 to Sun et al., ACOUSTIC DISPENSER ; Pat. No. 5,846,595 issued 08-Dec-98 to Sun et al., ELECTROSTATIC CHUCKS ; Pat. No. 5,858,814 issued 12-Jan-99 to Sun et al., ELECTROSTATIC CHUCKS ; Pat. No. 5,871, 010 issued 16-Feb-99 to Datta et al., INHALER APPARATUS WITH MODIFIED SURFACES FOR ENHANCED RELEASE OF DRYPOWDERS.

The following U. S. patent applications are of interest: S. N. 08/659,501 filed 06- Jun-1996 by Pletcher et al., METHOD AND APPARA TUS FOR ELECTROSTA TICALL Y DEPOSITING A MEDICAMENT POWDER UPON PREDEFINED REGIONS OF A SUBSTRATE, now Patent No. 6,007,630 issued 28-Dec-99; S. N. 08/733,525 filed 18-Oct- 96 by Pletcher et al., METHOD AND APPARATUS FOR ELECTROSTATICALLY DEPOSITING A MEDICAMENTPOWDER UPONPREDEFINED REGIONS OF A SUBSTRATE, now Patent No. 6,074,688 issued 13-Jun-00 ; S. N. 08/956,348 filed 23-Oct- 97 by Loewy et al., DEPOSITED REAGENTS FOR CHEMICAL PROCESSES, now Patent No. 6,004,752 issued 21-Dec-99; S. N. 08/956,737 filed 23-Oct-97 by Loewy et al., SOLID SUPPORT WITH ATTACHED MOLECULES, now Patent No. 6,045,753 issued 04-Apr-00 ; S. N. 09/026,303 filed 19-Feb-98 by Sun, BEAD TRANSPORTER CHUCKS USING REPULSIVE FIELD GUIDANCE, now Patent No. 6,096,368 issued 01-Aug-00 ; S. N.

09/047,631 by Sun, BEAD MANIPULATING CHUCKS WITH BEAD SIZE SELECTOR, now Patent No. 5,988,432 issued 23-Nov-99; S. N. 09/083,487 filed 22-May-98 by Sun, FOCUSED ACOUSTIC BEAD CHARGER/DISPENSER FOR BEAD MANIPULATING CHUCKS, now Patent No. 6,168,666 issued 01-Jan-01 ; S. N. 09/095,425 filed 10-Jun-98 by Sun et al., AC WA VEFORMS BIASING FOR BEAD MANIPULATING CHUCKS, now Patent No. 6,149,774 issued 21-Nov-00 ; S. N. 09/095,321 filed 10-Jun-98 by Sun et al., APPARATUS FOR CLAMPING A PLANAR SUBSTRATE ; S. N. 09/095,616 filed 10-Jun-98

by Chrai et al., PHARMACEUTICAL PRODUCT METHOD OF MAKING ; and S. N.

09/095,246 filed 10-Jun-98 by Desai et al., DRYPOWDER DEPOSITIONAPPARATUS, now Patent No. 6,063,194 issued 16-May-00.

Field of the Invention The present invention relates generally to unit dosage or unit diagnostic forms and an apparatus and method for making such unit forms.

Background of the Invention In the pharmaceutical industry, pharmaceutical products including diagnostic products comprise a container (e. g., a bottle, a blister pack or other packaging) containing a plurality of"unit dosage forms"or"unit diagnostic forms."Each of such unit forms contains a pharmaceutically-or biologically-active ingredient or ingredients and inert or inactive ingredient (s).

The pharmaceutically-active ingredient typically forms a drug. The diagnostic form may comprise a reagent or the like for use in diagnostic tests, and may be part of a set which includes several different reagents or active ingredients. Moreover, the diagnostic form may comprise an antibody, an antigen, or labeled forms thereof and the like.

A pharmaceutically-or biologically-active ingredient for use in a unit form may be supplied as a powder comprising a plurality of active-ingredient particles. Such active- ingredient particles are combined with inert or inactive ingredient particles to form a plurality of"major particles."The major particles are quite small, with dimensions on the order of microns. Such major particles are typically combined with one another to create the final unit dosage or diagnostic form (e. g., tablet, caplet, test strip, capsule, etc.).

There may be significant variation in the amount of pharmaceutically-or biologically-active ingredient in one major particle and the next. Since a large number of major particles are required to create a final unit form, the aforedescribed particle-to- particle variation may result in a substantial variation in the amount of active ingredient between one unit form and the next. Thus, any given final form may contain substantially more or less than a desired amount of active ingredients.

Destructive analytical screening procedures are conventionally performed to assess

the amount of active ingredient (s) in final unit forms. Since such procedures destroy the unit forms, a statistical sampling is performed whereby a relatively small number of forms per batch are actually sampled and tested. Such screening procedures disadvantageously provide no assurance that all forms in a given batch contain a desired amount of the pharmaceutically-or biologically-active ingredients. In fact, such statistical methods practically"guarantee"that a statistically determinable percentage of the forms in each batch will be out of specification.

As such, the art would benefit from a method and apparatus that provides improved control over the active-ingredient content of unit dosage and diagnostic forms.

Summary of the Invention In one embodiment, the present invention provides a product comprising a plurality of pharmaceutical unit dosage forms or unit diagnostic forms (collectively,"unit forms").

Each form includes at least one active ingredient that is present in an amount that advantageously does not vary by more than about five percent from a predetermined target amount.

In one embodiment, the unit form comprises a substrate, an active ingredient deposited thereon, and a cover layer that covers the active ingredient and is joined (e. g., via welding, adhesives, etc.) to the substrate in the proximity of the active ingredient.

In the illustrated embodiments, the product is made via a dry deposition apparatus that deposits powder/grains on the substrate. In one embodiment, the apparatus comprises an electrostatic chuck, a charged powder delivery apparatus, and an optical detection system. The substrate is engaged to the electrostatic chuck for the dry deposition of powder.

The chuck has at least one collection zone at which a powder-attracting electrical field is developed. The charged powder-delivery apparatus directs charged powder for electrostatic deposition to the substrate at the collection zone (s). The optical detection system quantifies the amount of powder deposited.

In some embodiments, the dry deposition apparatus also includes an electronic processor for controlling depositions responsive to sensor inputs. Such sensor inputs advantageously include one or more deposition sensors that are disposed on or adjacent to the electrostatic chuck and that provide data pertaining to the amount of powder deposited.

Responsive to sensor data, the electronic processor adjusts deposition parameters, as necessary. Controllable parameters include powder flux through the powder-delivery apparatus and applied voltage at the collection zone (s).

In still other embodiments, the present dry deposition apparatus advantageously includes a variety of other elements that are described in detail later in this Specification.

Brief Description of the Drawings FIG. 1 depicts an isometric view of a product comprising a strip package containing a plurality of unit forms in accordance with an illustrated embodiment of the present invention.

FIG. 2 depicts a cover layer of a strip package partially separated from a substrate.

FIG. 3 depicts a side view of an illustrative unit form in accordance with the present teachings.

FIG. 4 depicts a top view of the illustrative unit form of FIG. 3.

FIG. 5 depicts a packaging container for storing the product of FIG. 1.

FIG. 6 is a figurative depiction of an apparatus for making the present product.

FIG. 7 depicts a top view of a robotic platform in accordance with an embodiment of the present invention.

FIG. 8 depicts a side elevation of the robotic platform of FIG. 7.

FIG. 9 figuratively depicts, via side-elevation, an embodiment of a robotically- operated receiver and an electrostatic chuck for carrying a substrate upon which the unit forms are deposited.

FIG. 10 depicts a plan view of a first surface of an illustrative electrostatic chuck.

FIG. 11 depicts a plan view of a second surface of an illustrative electrostatic chuck.

FIGS. 12a-12c depict side cross-sectional views of embodiments of the electrostatic chuck of FIGS. 10 and 11 near a collection zone.

FIG. 13 depicts a front elevation of the receiver and electrostatic chuck shown in FIG. 9, and further depicts an illustrative arrangement for electrically connecting the electrostatic chuck to a circuit board in the receiver.

FIG. 14 depicts a side view of an illustrative lower pin assembly useful for connecting the electrostatic chuck to a circuit board in the receiver.

FIG. 15 depicts a gasket disposed between the electrostatic chuck and the receiver.

FIG. 16 depicts a top view of the illustrative lower pin assembly of FIG. 14.

FIG. 17 depicts the underside the illustrative receiver with the electrostatic chuck adhered thereto.

FIG. 18 depicts the underside the illustrative receiver without the electrostatic chuck.

FIG. 19 depicts a receiver platform for supporting components that comprise the receiver.

FIG. 20 depicts the receiver platform supporting several electronic components.

FIGS. 21 & 22 depict further details of the receiver and the manner in which it is engaged to the robotic transport element.

FIG. 23 depicts a lamination support block for laminating the substrate and cover layer together.

FIG. 24 depicts a deposition engine for electrostatically depositing powder on a substrate.

FIGS. 25 and 26 depict a rotatable baffle for use in dispersing the powder at a powder deposition station.

FIG. 27 depicts an illustrative powder trap for capturing powder that does not deposit.

FIGS. 28 and 29 depict an alternative embodiment of a receiver, electrostatic chuck and deposition station in accordance with the present teachings.

FIG. 30 depicts a first alternative embodiment of a powder feed apparatus.

FIG. 31 depicts a second alternative embodiment of a powder feed apparatus.

FIG. 32 depicts powder measurement via a diffuse reflection methodology.

FIG. 33 depicts powder measurement via an optical profilometry methodology.

FIG. 34 depicts a first measurement apparatus capable of both diffuse reflection and optical profilometry based-measurements.

FIG. 35 depicts the operation of the apparatus of FIG. 34 operating according to diffuse reflection methodology.

FIG. 36 depicts the operation of the apparatus of FIG. 34 operating according to optical profilometry methodology.

FIG. 37 depicts a second measurement apparatus capable of both diffuse reflection and optical profilometry based-measurements.

FIG. 38 depicts a plot that was developed based on data obtained using diffuse

reflection measurements.

FIG. 39 depicts a sealing head that is positioned over a substrate and a cover layer in preparation for laminating them together.

FIG. 40 depicts a first illustrative equivalent circuit diagram for AC-biased charge and deposition sensing for a collection zone.

FIG. 41 depicts plots of waveforms of voltages measured at a floating pad electrode and a collection zone.

FIG. 42 depicts a second illustrative equivalent circuit diagram for AC-biased charge and deposition sensing for a collection zone.

FIGS. 43a-43c depict an illustrative method based on blow-fill-seal technology for fabricating a final dosage form.

FIG. 43d depicts an illustrative final dosage form produced from the method of FIGS. 43a-43c.

FIGS. 44a-44b depict a further illustrative method for fabricating a final dosage form.

FIG. 44c depicts an illustrative final dosage form produced from the method depicted in FIGS. 44a-44b.

FIG. 45a depicts an additional method for fabricating a final dosage form.

FIG. 45b depicts an illustrative final dosage form produced from the method depicted in FIG. 45a.

FIG. 46 depicts an illustrative embodiment of a final dosage form suitable for providing timed release of a plurality of unit forms contained within the final dosage form.

FIG. 47 depicts a further illustrative embodiment of a final dosage form suitable for providing timed release of a plurality of unit forms contained within the final dosage form.

FIG. 48 depicts a bi-layer substrate.

FIG. 49 depicts a method for making the bi-layer substrate of FIG. 48.

Detailed Description The following terms shall have the respective meanings set forth below for the purposes of this description and the appended claims.

Dielectric or non-conductive refers to materials that are non-conductive to a degree

that distinguishes them from conductive materials such as copper and the like. The degree of non-conductance can vary considerably with context.

Dry deposited refers to depositing a material without using a liquid vehicle.

Effective amount means an amount effective to (1) reduce, ameliorate or eliminate one or more symptoms of a subject disease; (2) induce a pharmacological change relevant to treating a subject disease; or (3) prevent or lessen the frequency of occurrence of a subject disease, or symptoms thereof.

Electro-attractive dry deposition refers to methods that use an electromagnetic field, or an electrostatically-charged surface to dry deposit charged powder.

Grains are aggregates of either molecules or particles, such as the particles comprising a powder, or polymer structure that can be referred to as"beads."Beads can be coated, have adsorbed molecules, have entrapped molecules, or otherwise carry other substances. The particles or molecules of a powder have an average diameter that is typically at least about 1 nanometer (nm), and more typically in the range of about 100 nm to about 500 nm. Grains have a diameter that is in the range of about 100 nm to about 5 millimeters (mm), and more typically at least about 500 nm or 800 nm in average diameter.

Planar substrate denotes a substrate having two major dimensions, such as a tape or a sheet. While in some embodiments, planar substrates are flat, they need not be.

Unit form (pharmaceutical dosage or diagnostic) includes one or more discrete active ingredients (whether or not on a separate substrate and whether or not the substrate is edible) that can be used as a dosage for pharmaceutical purposes or as an element (s) for diagnostic purposes, whether or not encapsulated, whether or not capable of being packaged or otherwise available for end use as a unit.

Product and Unit Form FIG. 1 depicts a product 1 in accordance with an illustrative embodiment of the present invention. Product 1 comprises a package 2 that is realized as a strip 4 having an array of unit dosage forms 6. Strip 4 comprises a substrate 8 and a cover layer 9.

Substrate 8 and cover layer 9 each comprise a substantially planar, flexible film or sheet. In some embodiments, one of either substrate 8 or cover layer 9 includes an array of semi-spherical bubbles, concavities, blisters or depressions (hereinafter"bubbles") 12 that

are advantageously arranged in columns and rows. In the illustrative package depicted in FIG. 1, cover layer 9 comprises a three-by-five array of such bubbles 12, although more or fewer bubbles may suitably be provided. Substrate 8 and cover layer 9 are advantageously formed to have a thickness of about 0.001 inches (0.0254 mm) and typically comprise a thermoplastic material. Materials suitable for use as substrate 8 and/or cover layer 9 include, without limitation, polyvinylacetate, hydroxypropylmethylcellulose and polyethylene oxide films. Polyvinylacetate films suitable for use as the substrate and/or cover layer are commercially available from Polymer Films, Inc. of West Haven, CT; Chris Craft of Gary, IN; Aquafilm of Winston-Salem, NC; Idroplast S. p. A. of Montecatini Terme (PT), Italy; AICello Chemical Co., Ltd. of Toyohashi ; Japan; and Soltec of Paris, France.

As depicted in FIG. 2 (showing cover layer 9 partially"peeled"back from substrate 8) and FIG. 3, a deposit of a dry active ingredient 14, in the form of powder (s)/grains (hereinafter,"powder,") is disposed between substrate 8 and cover layer 9 within a bubble 12. In some embodiments, active ingredient 14 is a pharmaceutical product, such as a drug; in other embodiments, active ingredient 14 is a diagnostic product that is useful for biological diagnostic laboratory or medical related purposes. The method and means by which active ingredient 14 is deposited on substrate 8 is described later in this specification.

As used herein, the term"powder"signifies a single (i. e., one type of) powder as well as multiple (i. e., different types of) powders.

As depicted via a cross-sectional view in FIG. 3 and plan view in FIG. 4 (each showing only a single bubble 12), substrate 8 and cover layer 9 are attached to one another via bonds or welds 7 that are near to and encircle bubble 12. Bonding can be effected, for example, via heat or ultrasonic welding or via suitable adhesives. Unit form 6 comprises a deposit of active ingredient 14, bubble 12, and a region of substrate 8 within bonds 7.

As depicted in FIG. 5, strips 4 containing unit forms 6 can be provided, for example, in a box 16 or like packaging container, for the convenience of a user.

Unit dosage forms 6 in accordance with the present teachings can be used to form a variety of final dosage forms. Illustrative final dosage forms incorporating one or more unit dosage forms 6 are described later in this specification after various embodiments of an apparatus for making unit dosage forms 6 are described.

Apparatus for Making the Present Product FIG. 6 depicts, conceptually, the elements of an apparatus 100 suitable for making the present product. Apparatus 100 comprises platform 101 wherein the unit forms in accordance with the present invention are created. Platform 101 is advantageously adapted for robotic operation, as depicted in the illustrative embodiments. In other embodiments, however, platform 101 is not robotic. In such other embodiments, platform 101 includes, for example, manually-operated mechanisms (e. g., gantry and crane) for retrieval and transit of substrates, etc. Platform 101 creates such unit forms via a variety of operations, chief of which is the electrostatic deposition of dry powder on defined discrete regions of a substrate.

Additional operations include some or all of the following: materials handling, alignment, dose measurement and lamination.

Electrostatically-charged powder is delivered to robotic platform 101 via powder feed apparatus 801. Processor 401 and controller 403 control various electronic functions of apparatus 100, such as, for example, the application of voltage for the electrostatic deposition operation, the operation of powder feed apparatus 801, the operation of robots that are advantageously in conjunction with platform 101, and dose measurement operations.

Memory 405 is accessible to processor 401 and controller 403.

In some embodiments, platform 101 and/or powder feed apparatus 801 are isolated from the ambient environment by an environmental enclosure. In such environments, environmental controller 901 provides temperature, pressure and humidity control for robotic platform 101 and powder feed apparatus 801.

A detailed description of the aforementioned elements of apparatus 100 is provided below.

The Platform and the Operation Thereof FIGS. 7 and 8 depict a top view and a front elevational view, respectively, of illustrative platform 101. Four supports 104 are disposed one at each corner of platform 101. Supports 104 elevate support bench 110 and various structures associated with platform 101 above a table or like surface. Additionally, supports 104 advantageously provide a frame or superstructure for optional side-mounted barriers 106, depicted in FIG. 7.

Side mounted barriers 106 may be comprised of glass, polycarbonate or acrylic panes and the

like. The side-mounted barriers, in conjunction with a top barrier (not shown) and support bench 110 define an environmental enclosure or chamber 102 that isolates the region therein from the ambient environment under air or inert gas.

Support bench 110 comprises five processing stations that perform various operations advantageously used to produce the present product. Briefly, those processing stations include: input/output station 120, advantageously comprising three substations 120A, 120B and 120C, for storing substrates and cover layers; alignment station 130 for assuring that the substrate and cover layer are properly aligned to their transport mechanism; deposition station 150 where powder are deposited on the substrate; dose measurement station 140 for measuring the amount of powder that is deposited on the substrate; and lamination station 160 where the cover layer is laminated to the substrate.

In the illustrated embodiment, platform 101 is adapted for robotic operation by way of first robotic transport element 170 and second robotic transport element 180. A receiver 172 is attached to first robotic transport element 170. Receiver 172 is operable, as discussed in further detail later in this specification, to retrieve at least the substrate from substation 120C and to move it to at least some of the various operational stations 130-160 for processing. A"bonding"head 182 is attached to second robotic transport element 180.

Bonding head 182 is operable, as discussed in further detail later in this specification, to join/seal the substrate and cover layer to one another.

Robotic transport elements 170 and 180 are movable (e. g., to access different processing stations) along first rails 190 that provide guides for motion in one direction (e. g., along the x-axis). Additional rails (not shown) movably mounted on first rails 190 provide guides/support for motion in a direction orthogonal (e. g., the y-axis) to first rails 190, to provide x-y motion. Drive means (not shown), such as x-y stepper motors, move robotic transport elements 170 and 180 along the rails. First and second robotic transport elements 170 and 180 have telescoping components under servo control (not shown) that provide movement along the z axis (i. e., normal to the x-y plane). Such z-axis movement allows receiver 172 or bonding head 182 to move"downwardly"toward a processing station to facilitate an operation, and"upwardly"away from a processing station after the operation is completed. Robotic transport elements 170 and 180 advantageously include 9 control components under servo control (not shown) that allow receiver 172 and bonding head 182 to be rotated in the x-y plane as may facilitate operations at a processing station. Compressed

dry air or other gas is suitably provided, such as at a flow rate of 8 SCFM at 80 psi, to operate the robotic transport elements. Robotic transport elements 170 and 180 can be based, for example, on a Yaskawa Robot World Linear Motor Robot available from Yaskawa Electric Company of Japan.

The following disclosure provides a description of embodiments of various elements and features of apparatus 100. To provide perspective for such disclosure, a summary of at least one embodiment of the operation of apparatus 100 is first presented.

In operation, first robotic transport element 170 moves receiver 172 and an engaged electrostatic chuck 202 (used for powder deposition, see, FIGS. 9-11, etc.) to input/output station 120. At station 120, the electrostatic chuck engages substrate 80 and, in some embodiments, also engages a frame 81 that is joined to the substrate. In one embodiment, robotic transport element 170 then moves the engaged receiver 172, electrostatic chuck 202, substrate 80 and frame 81 to alignment station 130. At the alignment station, frame 81 is re- aligned to electrostatic chuck 202 via various alignment mechanisms, thereby improving the accuracy and consistency of alignment of substrate 80 with electrostatic chuck 202.

Robotic transport element 170 then moves engaged receiver 172, electrostatic chuck 202, substrate 80 and frame 81 to dose measurement station 140. After aligning with a measurement apparatus at station 140, substrate 80 is scanned via a measurement device and distances from a reference point to substrate 80 at each of a plurality of"collection zones" CZ (see FIG. 10) are calculated and recorded to provide baseline data.

Robotic transport element 170 then moves engaged receiver 172, electrostatic chuck 202, frame 81 and"virgin"substrate 80 to deposition station 150. At deposition station 150, the powder deposition engine (see FIGS. 23-29) is turned on and powder is electro- deposited at collection zones CZ.

At the completion of the powder-deposition operation, robotic transport element 170 returns substrate 80, with its complement of deposited powder, to dose measurement station 150. At station 150, the measurement device again scans substrate 80 to determine the distance between the reference point to the surface of the"deposit"of powder accumulated at each collection zone CZ. From such distances, and the previously obtained baseline data, the amount (e. g., volume) of powder deposited at each collection zone is calculated. If the calculated amount is outside a desired range of a predetermined target amount, such information is displayed. An operator can then suitably adjust operating parameters to bring

the process back into specification. In another embodiment, automatic feed back is provided to automatically adjust the process, as required. The"out-of-spec"unit forms may be discarded.

Second robotic transport element 180 picks up cover layer 90 and frame 91 from input/output station 120 and delivers them to lamination station 160. After measurements are completed at dose measurement station 150, first robotic transport element 170 delivers substrate 80 with its complement of powder to lamination station 160. Substrate 80 is placed, via first robotic transport element 170, on cover layer 90 such that the deposits of powder are properly aligned within the perimeter of the blisters or bubbles in the cover layer.

After first robotic transport element 170 moves away, second robotic transport element 180 returns and, by the operation of bonding head 182, welds the substrate and cover layer together, forming a plurality of unit forms on a strip (see, FIG. 1). In an automated system, the unit forms may be automatically transferred to a packaging station wherein out- of-specification unit forms are screened out and in-spec unit forms are appropriately packaged.

The present method and apparatus provide a product containing a plurality of pharmaceutical or diagnostic unit forms, each comprising at least one pharmaceutically or diagnostic active ingredient that advantageously does not vary from a predetermined target amount by more than 5%.

Having provided an overview of an embodiment of the present invention, further detailed description of illustrative embodiments of various elements and features of apparatus 100 and the operation thereof are now provided.

The Receiver, Electrostatic Chuck and Substrate Assembly In accordance with the present invention, powder comprising an active ingredient is electrostatically deposited at discrete locations on substrate 80 at deposition station 150. In the illustrated embodiments, accomplishing such deposition requires that, among other things, substrate 80 is transported to deposition station 150 from some other location, and that an electrostatic charge is developed that causes the powder to electrostatically deposit on substrate 80. Such transport and charging operations are facilitated, at least in part, via receiver 172 and electrostatic chuck 202. Before providing a detailed description of such

elements, an overview of the cooperative relation between receiver 172, electrostatic chuck 202 and substrate 80 is provided below in conjunction with FIG. 9.

FIG. 9 is a simplified representation that depicts receiver 172 engaged to electrostatic chuck 202. Illustrative receiver 172 comprises electronics housing 1610, vacuum manifold housing 1620, and gasket 1630, interrelated as shown. Electrostatic chuck 202 is engaged to receiver 172 against gasket 1630. Substrate 80 (not shown in FIG. 9) is releaseably secured to electrostatic chuck 202. Electronics housing 1610 includes circuitry, described in more detail later in this specification, for controlling the operation of electrostatic chuck 202.

Reduced pressure (e. g., partial vacuum) is applied to passageways 1622 of vacuum manifold housing 1620 via inlet fitting 1621 and a passageway outlet (not shown).

Passageways 1622 convey reduced pressure to"through holes"in electrostatic chuck 202 (not shown in FIG. 9; see through holes ECH in FIGS. 10 and 11). Substrate 80 is in turn exposed to such reduced pressure via openings in gasket 1630 (not shown in FIG. 9, see slots 1631 in FIG. 15). The reduced pressure releaseably secures the substrate to electrostatic chuck 202. Further detailed description of receiver 172, electrostatic chuck 202 and substrate 80 and cover layer 90 is provided below.

In the illustrated embodiments, the substrate and cover layer are stored at input/output substations 120A, 120B and 120C, and are advantageously mounted on frames.

More particularly, substrates 80 are advantageously mounted on frames 81 forming substrate assemblies 82, and cover layers 90 are advantageously mounted on frames 91 forming cover assemblies 92. As depicted in FIGS. 2 and 3, substrate 80 is a planar film and cover layer 90 is a substantially planar, flexible film having an array of semi-spherical bubbles or blisters that are advantageously arranged in columns and rows.

In the illustrative embodiment depicted in FIG. 7, first input/output substation 120A contains substrate assemblies 82, second input/output substation 120B contains cover assemblies 92, and third input/output substation 120C contains interlocked frames 81 and 91 containing substrates 80 and cover layers 90 after bonding/lamination.

As described further below, frames 81 and 91 advantageously aid in aligning the substrates 80,90 to various elements of apparatus 100. The frames are made of a suitably strong material that is preferably"light weight,"such as, for example, aluminum. Frames having a rectangular shape with the shorter sides measuring about 200 mm and the longer sides measuring about 300 mm, and all sides having a thickness of about 12.7 mm have

found to be suitable for use in conjunction with the present invention.

FIG. 10 depicts a view of first surface 204 of electrostatic chuck 202. Electrostatic chuck 202 comprises a layer 203 of dielectric material such as, for example, Kaptont) brand polyimide film commercially available from Dupont de Nemours, Wilmington, DE. The electrostatic chuck has a thickness of about 0.01 inches (0.25 mm), and, as such, is relatively flexible. Illustrative electrostatic chuck 202 has"through holes"ECH implemented as slots that are disposed at its periphery. Other suitable configurations for electrostatic chuck "through holes"are illustrated in U. S. Pat. App. No. 09/095,321. First surface 204 further includes a plurality of powder collection zones CZ. In illustrative electrostatic chuck 202, collection zones CZ are advantageously organized in eight columns 207Cl C8 of twelve collection zones each for a total of ninety-six collection zones CZ. As will be described further later in this specification, each collection zone CZ corresponds to a powder deposition location on the substrate (see substrate 8 in FIG. 1). Collection zones CZ are formed within electrostatic chuck 202 by an arrangement of dielectric and conductive regions, several embodiments of which are described later in this specification in conjunction with FIGS. 12a-12c.

FIG. 11 depicts a view of second surface 206 of electrostatic chuck 202. As depicted in more detail in FIGS. 12a-12c, collection zones CZ are formed via electrical contact pads 208. Such electrical contact pads 208 provide contact points for connection to a controlled voltage source. Electrical contact pads 208 are electrically connected to selected other electrical contact pads via address electrodes 210.

By virtue of discrete electrical contact pads 208, and address electrodes 210 that electrically connect select groupings of such contact pads (e. g., the pads 208 within a given column 207c, C8 of illustrative chuck 202 of FIG. 11 define an illustrative grouping), a first voltage can be applied to contact pads 208 in column 207Cl, while a second voltage different from the first voltage can be applied to contact pads 208 in second column 207C2, and so forth varying the voltage applied to contact pads 208 on a column-by-column basis as desired. It will be understood that the application of such different voltages to such different columns results in depositing a different amount of powder at collection zones CZ in each of such columns. It will be appreciated that in other embodiments, address electrodes are arranged differently thereby creating electrical interconnects between differently arranged groupings of contact pads 208. For the layout of contact pads 208 and address electrodes 210

depicted in FIG. 11, voltage need only be applied to a single contact pad 208 within a given column 203 for substantially the same electrostatic charge to be developed at each contact pad 208 within that column.

FIGS. 12a-12c depict several illustrative embodiments of structural arrangements suitable for forming collection zones CZ within an electrostatic chuck, such as electrostatic chuck 202. For clarity of illustration, the structure associated with only a single collection zone CZ of an electrostatic chuck is depicted in FIGS. 12a-12c.

In a first embodiment depicted in FIG. 12a, a conductive material 305 is disposed through layer 303 of dielectric at each region designated to be a collection zone CZ. The conductive material overlays a portion of first surface 304 and second surface 306 of the electrostatic chuck. The portion of conductive material 305 overlying first surface 304 comprises a powder-attracting electrode 307A, while the portion of conductive material 305 overlying the second surface 306 comprises electrical contact pad 308A (equivalent to the electrical contact pads previously described, such as contact pad 208 depicted in FIG. 11). A shield electrode 312 (also termed a"ground electrode"based on a preferred bias) is disposed within layer 303.

Applying a voltage to electrical contact pad 308A generates an electrostatic field at powder-attracting electrode 307A at collection zone CZ. As described later in this specification, the electrostatic field attracts charged powder to the substrate (e. g., substrate 380). Additionally, the electrostatic field aids in holding substrate 380 flat against first surface 304 of the electrostatic chuck. The reduced pressure that is developed in vacuum manifold housing 1620 (see FIG. 9) to which substrate 380 is exposed also assists in adhering substrate 380 to the electrostatic chuck. Tight adherence of the substrate 380 to the electrostatic chuck increases the reliability of powder deposition at the collection zones.

FIG. 12b depicts a second illustrative embodiment where through holes ECH are formed at electrical contact pad 308B and powder-attracting electrodes 307B. FIG. 12c depicts a third illustrative embodiment wherein an additional layer 314 of dielectric material separates powder-attracting electrode 307C from base substrate 380. Electrical contact-pad 308C overlays second surface 306 of layer 303.

The electrostatic chuck provided by the configuration depicted in FIG. 12c can be termed a"Pad Indent Chuck"which is useful, for example for powder depositions of less than about 2 mg, preferably less than about 100 pg, per collection zone CZ (assuming, for

example, a collection zone having a diameter within the range of 3-6 mm diameter). The electrostatic chuck provided by the configuration depicted in FIG. 12a can be termed a"Pad Forward Chuck"which is useful, for example, for powder depositions of more than about 20 gg per collection zone CZ (again assuming a collection zone of about 3-6 mm diameter). The Pad Forward Chuck is more useful than the Pad Indent Chuck for higher dose depositions.

It should be clear from earlier description that a voltage source must be electrically connected to the powder-attracting electrodes (hereinafter generically identified by the call- out"307"). An illustrative arrangement for providing such connection is depicted in FIG. 13, which depicts receiver 172 engaged to electrostatic chuck 202 as in FIG. 9, but viewed from the perspective indicated by the arrows identified as"13"in FIG. 9.

Electrical connection to powder-attracting electrodes 307 is effected via coupled pins 1623. Each coupled pin 1623 comprises a pin 1627 and a lower pin assembly 1624. Pin 1627 is advantageously a standard circuit board pin. As depicted via side view in FIG. 14, lower pin assembly 1624 has a slot 1625 for receiving pin 1627 (not shown). Pins 1627 couple with slots (not shown) on pin connector board 1611. As described in further detail later in this specification, pin connector board 1611 is electrically connected to a controlled voltage source. The coupled pins 1623 pass through holes (not shown) in electronics housing 1610, holes (not shown) in vacuum manifold housing 1620 and holes 1632 (see FIG. 15) in gasket 1630 to contact the electrical contact pads (not shown in FIG. 13) of electrostatic chuck 202. Such electrical contact pads are depicted, for example, in FIG. 11, as pads 208 located on second surface 206 of electrostatic chuck 202 (see also, pads 308A-308C of FIGS.

12a-12c).

A conductive adhesive, such as conductive epoxy, is applied to a lower region of lower pin assemblies 1624 such that the adhesive adheres the lower pin assemblies to the electrical contact pads. Notch 1626 in lower pin assembly 1624, as shown in a top view of lower pin assembly 1624 depicted in FIG. 16, allows excess conductive adhesive to be displaced from the region at which the lower pin assembly contacts the electrical contact pad.

The above-described arrangement for providing electrical connection to powder- attracting electrodes 307 advantageously avoids deforming electrostatic chuck 202, which in most embodiments is relatively susceptible to deformation. It is advantageous to avoid such deformation because, if the electrostatic chuck deforms, then the substrate adhered thereto will likewise deform. Deformation of the substrate is undesirable because it is preferable to

deposit powder on a"flat"substrate. Thus, while other arrangements for providing electrical connection to the powder-attracting electrodes, as may occur to those skilled in the art in view of the present teachings, may suitably be used, such arrangements will advantageously avoid deforming the electrostatic chuck.

Gasket 1630, depicted in FIG. 15, includes slots 1631 that allow reduced pressure to be transmitted to electrostatic chuck 202. Gasket 1630 further includes holes 1632 that allow coupled pins 1623 to be inserted through the gasket 1630, as previously described. Gasket 1630 preferably insulates at least about 2,000-2,500 volts. In one embodiment, gasket 1630 is coated on both sides with adhesive. A material suitable for use as gasket 1630 is a graphics art paper having a thickness of 0.004 inches (0.1 mm) that is coated on both sides with an aggressive rubber-based adhesive. Such paper is commercially available from Cello- Tak of Island Park, New York.

FIGS. 17-22 depict additional detail of an illustrative embodiment of receiver 172, and an arrangement for connecting the receiver to first robotic transport element 170.

FIG. 17 depicts underside 1730 of receiver platform 1720 of illustrative receiver 172 with electrostatic chuck 202 adhered thereto. Electrostatic chuck 202 has alignment features 240, such as pins or holes, by which it is aligned to complementary holes or pins 1629 in receiver platform 1720 (see FIG. 18). Also depicted are alignment pins 1650 that are received by complementary holes in support bench 110 for aligning receiver 172 to various processing stations (e. g., deposition station 150). Height-adjustable vacuum cups 1670 are advantageously used to attach the substrate frame (not shown) to the receiver.

FIG. 18 depicts underside 1730 of receiver platform 1720 without electrostatic chuck 202. FIG. 18 shows passageways 1622 for conveying reduced pressure to through holes ECH in electrostatic chuck 202 (through holes ECH not shown in FIGS. 17 and 18; see FIGS. 10 and 11) and to passageway outlet 1628. Pin conduits 1623A allow passage of coupled pins 1623 to electrical contact pads on electrostatic chuck 202. Further shown are alignment features 1629, which can be, for example, alignment pins or alignment pin receptacles for mating with alignment features 240 of electrostatic chuck 202.

FIG. 19 shows upper side 1710 of receiver platform 1720. Receiver platform 1720 includes passageway outlet 1628, pin conduits 1623A and moldings that form reinforcing braces 1780. As illustrated in FIG. 20, braces 1780 on upper side 1710 support processor board 1614, addressing board 1615 and high-voltage board 1612 (i. e., bias-generation board).

Electrical communication to electronics located off of receiver 172 can be accomplished via port 1616. Tubing connector 1627B connects receiver 172 to an external vacuum source for developing reduced pressure through vacuum manifold housing 1620, etc., for adhering substrate assembly 82 to electrostatic chuck 202.

FIG. 20 also depicts a substrate frame, such as substrate frame 81, engaged to underside 1730 of receiver platform 1720 (electrostatic chuck not shown). Substrate frame 81 includes alignment features 52 that suitably engage complementary alignment features at alignment station 130.

FIGS. 21 and 22 depict an arrangement by which receiver 172 is engaged to robotic transport element 170 (depicted in FIG. 8), as well as showing additional features associated with receiver 172. FIG. 21 provides a"cutaway,"along the indicated perspective, of the view indicated in FIG. 22.

In the illustrative embodiment depicted in FIGS. 21 and 22, receiver 172 is mounted to first robotic transport element 170 (not shown) via bearing housing 1120. Bearing housing 1120 contains spline shaft 1121 and spline shaft bearings 1122. Bearing housing 1120 allows receiver 172 to be moved along the z-axis. Bearing housing 1120 couples to floating bolt assembly 1640 via spring-loaded coupling 1130. Floating bolt assembly 1640 (see FIG.

22) mounts to receiver cover 1660 via bushings 1641, which may be visco-elastic isolation bushings 1641. Such visco-elastic isolation bushings can be made, for example, from Sorbothane brand isolation damping material commercially available from Sorbothane, Inc. of Kent, OH. The visco-elastic isolation bushings 1641 advantageously allow receiver 172 to move slightly, as required, when receiver locating pins 1650 (see also FIG. 17) are inserted into alignment holes located on support bench 110. In this manner, the locating accuracy of robotic head 170 (2 mil) can be increased (to about 0. 5 mil) when base substrate 80 is presented for dry deposition at deposition station 150. Floating bolt assembly 1640 allows receiver 172 to comply with alignment actions acting in a direction along the x, y or z axes.

In the embodiment depicted in FIG. 21, receiver 172 includes pin connector board 1611, high-voltage board 1612, high-voltage chip areas 1613 and processor board 1614. In other embodiments, processing is orchestrated via a processor located elsewhere on robotic platform 101. High-voltage barrier wall 1661 isolates the high voltage areas of receiver 172.

Illustrative receiver 172 further includes vacuum tubing 1627, first tubing connector 1627A for connecting vacuum tubing 1627 to vacuum manifold housing inlet fitting 1621 (see FIG.

9), and second tubing connector 1627B previously described.

Substrate frame 81, on which substrate 80 is mounted, is depicted as adhered to the underside of the receiver 172 (electrostatic chuck 202 not shown). As discussed further below, the frame advantageously assures that the substrate is aligned with a post-deposition measurement device. Vacuum cup receiving fixtures 51, which are disposed on substrate frame 81, receive height adjustable vacuum cups 1670 in vacuum-facilitated engagement.

Vacuum hose fittings 1671, which are connected to a vacuum system, are in fluid communication with vacuum cups 1670.

Portions of receiver 172 (e. g., receiver cover 1660 in FIG. 22) are advantageously manufactured from a durable non-conductive material such as, for example, plastic.

Examples of suitable plastics include Noryltt brand polymers commercially available from GE Plastics of Pittsfield, MA. Noryl engineered plastics are modified polyphenylene oxide, or polyphenylene oxide and polyphenylene ether, resins. Modification of these resins involves blending with a second polymer such as polystyrene or a mixture of polystyrene and butadiene. By varying the blend ratio and other additives, a variety of polymer grades are produced. Unmodified, these polymers are characterized by regular closely-spaced ring structures (i. e., phenyl groups) in the main molecular chain. This feature along with strong intermolecular attraction causes extreme stiffness and lack of mobility.

Use of Noryl (D brand plastics or equivalent imparts a strength to receiver 172 that aids in providing a firm, flat support for electrostatic chuck 202. The surface of receiver 172 on which electrostatic chuck 202 is mounted is advantageously machined flat, for example to 0.001 inches (0.025 mm). Moreover, the characteristic low weight of the plastic assists in keeping the weight burden low on first robotic transport element 170.

Electronic Control of the Electrostatic Chuck As previously described, apparatus 100 advantageously includes central processor 401 and controller 403 for performing calculations, control functions, etc. (see, e. g., FIG. 6).

Processor 401 receives performance input from multiple sources, including, for example, on- board sensors and historical data from dose measurement station 140, and uses such information to determine if operating parameters should be adjusted to keep powder deposition within specification. Such input includes, for example, data pertaining to the rate

of powder flux into and through the deposition engine (made up of powder feed apparatus 801 and deposition station 150) and the degree to which powder is being evenly deposited at electrostatic chuck 202. The"on-receiver"electronics described below, either alone or in conjunction with processor 401 and controller 403, provide a means for adjusting apparatus 100 during operation.

When processor 401 has primary responsibility for processing functions, processor board 1614 located in receiver 172 can function as a communications board that receives commands from processor 401 and relays such commands to addressing board 1615. In some embodiments, processor board 1614 receives data from sensors, such as charge sensor 1690, that are positioned on or adjacent to electrostatic chuck 202 (see FIG. 18, wherein charge sensor 1690 is represented figuratively by dashed lines). Charge sensor 1690 is an on- the-receiver device for monitoring the amount of powder being deposited. Processor board 1614 locally interprets and responds to data from charge sensor 1690 by suitably adjusting the voltage applied to the powder-attracting electrodes 307 (e. g., electrodes 307A-307C in FIGS. 12a-12c, respectively) as appropriate. Charge sensors are described further below and in U. S. Pat. App. 09/095,425, now Patent No. 6,149,774.

After receiving signals from processor board 1614, addressing board 1615 sends bias control signals, which can be, for example, DC or AC signals, for controlling the voltage at powder-attracting electrodes 307. Depending upon the addressing scheme (e. g., the arrangement, if any, by which individual electrical-contact pads 208 are electrically interconnected via address electrodes 210), voltage is either regionally (e. g., by columns, rows, etc.) or individually applied to powder-attracting electrodes 307.

Addressing board 1615 preferably has multiple channels of synchronized output (e. g., square wave or DC). The signals sent to the addressing board can be encoded, for example, with a pattern of square wave voltage pulses of varying magnitudes to identify a powder-attracting electrode 307, or a group of such electrodes, together with the appropriate voltage to be applied thereto.

The bias control signals are sent via high voltage board 1612, which advantageously has multiple channels of high-voltage converters (transformers or HV DC-to-DC converters) for generating the voltages, such as 200 V or 2,500 V or 3,000 V (of either polarity), that energizes powder-attracting electrodes 307. Such high voltages are advantageously formed within receiver 172 so that other systems are isolated therefrom.

The Charge Sensor The charge sensor 1690, mentioned above, advantageously uses pulsed (AC) electrical potential waveforms for biasing the electrostatic chuck to collect powder on substrate 80, as is described in U. S. Pat. App. No. 09/095,425. This form of biasing overcomes the problem of collecting powder on a conductive substrate, where the powder- attracting field can decay rapidly after any given application of a bias potential to the electrostatic chuck.

Using AC bias waveforms for the powder-attracting electrode also solves another long-standing problem during deposition sensing. In particular, during deposition sensing, one or more collection zones CZ are closely monitored for powder accumulation, so as to allow regulation of the powder deposition process (e. g., to produce precise dosages). Such monitoring can be performed optically or by measuring accumulated charge using an"on- board"charge sensor at a sensor-associated collection zone. Accumulated charge can be correlated to actual charged powder deposition by empirical data collection. In dry powder deposition, such dose monitoring is often a very difficult task, particularly for dosages below one milligram.

The difficulty lies not with the precision of the measuring devices, but rather with various practical and environmental factors that can deteriorate measurement sensitivity by two or three orders of magnitude. For quasi-static DC-biased transporter chucks, on-board charge sensing is particularly difficult. Data obtained by depositing on a polypropylene film substrate with different potentials indicates that the deposited dose is linearly related to the bias potential if that potential is above a certain threshold potential. Data indicates that threshold potential is about 100-200 volts DC, at least for certain transporter chucks.

FIG. 40 shows one possible equivalent circuit diagram that provides AC-biased charge and deposition sensing for at least one collection zone CZ, which zone has a floating pad electrode. The floating pad electrode is an isolated conductor which is designed to be capacitively coupled to a powder-attracting electrode (e. g., powder-attracting electrodes 307A-307C of FIGS. 12a-12c, respectively) such that the bias to the powder-attracting electrode indirectly creates a powder-attracting field emanating from the floating pad electrode.

An illustrative electrostatic chuck/substrate arrangement corresponding to the equivalent circuit of FIG. 40 includes a planar electrode that is used to provide a powder- attracting field. A bottom face of the planar electrode is affixed to an upper face of a planar first dielectric layer such that such faces are parallel to one another. Suitable dielectric material includes Pyrex 7740 glass available from Coming, Inc., or polyimide resin having a thickness of about 10 to 20 mils. The planar electrode and planar first dielectric layer can be affixed to one another using a variety of suitable methods such as, for example, lamination, powder deposition or thin film deposition. A planar shield electrode is affixed to a bottom face of the first dielectric layer. The shield electrode comprises an aperture to accommodate a floating pad electrode, coplanar with and surrounded by the shield electrode.

One or more collection zones CZ are typically dedicated solely for sensing or, alternatively, are in general use, but closely monitored. By measuring the lowering of the attraction potential VBCZ that occurs as charged powder deposits on the collection zone CZ, a measure of the deposited charge can be obtained. Knowing the average charge/mass ratio q/m of the deposited powder, the accumulated powder deposition mass can be determined.

Vgcz can be measured directly across a charge-collector electrode, but it is usually preferable to measure the potential across a coupling capacitor, such as the floating pad electrode described above.

The coupling capacitor, as embodied by the aforedescribed floating pad electrode, provides reasonably accurate reproduction of the potential at the collection zone CZ on the substrate surface. Such accurate reproduction is shown by examining waveforms 3602 for VBCZ and waveform 3604 for Vpad F depicted in FIG. 41. RC decay is evident in waveforms 3602 and 3604. Waveform 3606 represents the pulsed bias voltage Vg. Whether a charge collector or charge coupling capacitor is used, they may both be considered charge sensing electrodes.

In the equivalent circuit of FIG. 40, charge collector/coupling capacitor CC is electrically connected to a separate sensing capacitor SC. The voltage generated across sensing capacitor SC can be a reliable indicator of the potential VBCZ. Such voltage can be measured, for example, with an electrometer M, such as a Keithley model no. 614,6512, 617,642,6512, or 6517A electrometer, as shown schematically in the figure. Generally the coupling capacitor CC is any electrode that is capacitively coupled to a powder collection zone on the contact surface.

DC biasing can cause a steady drift in the reading of the potential across the sensing capacitor. Such drift is due predominantly to natural leakage across the dielectric material in the sensing capacitor, and to charge leakage in the substrate or powder that has accumulated on the chuck. Drift can also be induced by noise factors such as shot noise, Johnson (1/f) white noise, thermal noise, Galvanic noise, triboelectric noise, piezoelectric noise, amplifier noise, and electromagnetically-induced noise. See, The Art of Electronics, by Paul Horowitz, Winfield Hill, 2nd Edition, Cambridge University Press, t) 1989.

If the drift is large compared to the actual charge collected at a collection zone CZ, the accuracy of the charge sensor as a measurement tool can be unacceptably low. Using AC biased waveforms as disclosed herein advantageously reduces the incidence of drift. Such a reduction is accomplished in a manner similar to that described above for avoiding the"drift" of charge dissipation on the powder collection zone, facilitating precise measurement of charge collected.

In FIG. 40, an AC bias source B may be the same source as described above, with the AC bias potential applied or administered via the powder-attracting electrode. This electrically couples to the floating pad electrode or to the collection zone itself, if it is directly connected to the sensing capacitor as shown.

By way of example, if sensing capacitor SC is chosen to be 0.1 uF, and the q/m of the powder is 10pC/g, then a 100 mV signal change on the charge collector/coupling capacitor CC corresponds to 1 mg of powder deposited on the collection zone. If, for example, the linear correlation factor is 3, then 1 mg of powder on the sensor corresponds to 3 mg of powder in the actual deposition dose. A 99 pg actual dose will thus have a detectable potential change of 3.3 mV. With a 5% error tolerance, the corresponding background unpredictable noise contribution cannot exceed 160 uV. This is achievable with careful shielding and grounding design. Preferably the charge collector is integrated with the chuck design to assure a consistent correlation.

In effect, the same benefits obtained using the AC bias waveform for Vg to avoid charge dissipation in the substrate can be used to reduce drift in the charge sensing circuit.

FIG. 42 depicts another possible equivalent circuit for providing AC-biased charge and deposition sensing. The illustrative circuit of FIG. 42 reduces noise by separating the AC bias source B from electrometer M, sensing capacitor SC or charge collector/coupling capacitor CC. All of those components have a sensitivity to noise that is critical.

As depicted in FIG. 42, AC bias source B is connected to the primary of a transformer T. In this manner, only the periodic magnetic field generated by Vg, (not Vg itself) is introduced into the"sensitive"components on the right side of the figure. The secondary winding of transformer T is connected across a stabilizing bleed resistor R, with one pole (i. e., biasing pole BP) connected to charge collector/coupling capacitor CC, and the other pole (i. e., the sensing capacitor pole CP) connected to sensing capacitor SC. To further reduce noise, sensing capacitor SC is connected to ground. Electrometer M can then measure the voltage change on sensing capacitor SC with respect to ground, as shown. The two grounding points can be combined to further reduce electromagnetic noise. Transformer T can be a step-up transformer so that complex AC bias waveforms supplied here and to the powder-attracting electrode can be generated inexpensively. A step-up ratio of 50, for example, may suitably be used. Such an arrangement substantially reduces drift and makes accumulated charge sensing more accurate, where previously a coupling current of 100 pico- Amperes or less made drift and noise a problem.

In some embodiments, transformer T is an isolation transformer, where the primary and secondary windings are separated by a Faraday cage. This can prevent coupling between the primary and secondary windings, where the primary winding acts as one capacitor plate, and the secondary as the other capacitor plate.

As a result of the improved signal to drift ratio obtained in accordance with the present teachings, the amount of charge sensed can decrease substantially. Measurements can be made using a 1000 picoF capacitor as the sensing capacitor instead of the 0.1 of value used previously. Also, AC bias source B used in the circuits depicted in FIGS. 40 and 42 can be separate from the AC waveform bias Vg on the chuck, by delivering a separate AC bias directly to charge collector/coupling capacitor CC via a dedicated wire, electrode, bus, etc.

Such a separate AC bias can be frequency matched or detuned with respect to Vg to insure consistent correlation of the behavior of the charge collector/coupling capacitor CC to actual depositions.

The aforedescribed arrangements advantageously allow Vg biasing with voltage peaks much higher than previously possible. Using 8000 molecular weight polyethylene glycol as a substrate, bias peaks of 2 kV have been used. It should be understood a wide variety of transporter chucks can suitably be used, including those that operate with bias electrodes directly exposed to the powder contact surface (i. e., the substrate), such as is

illustrated in FIGS. 12a and 12b.

The Alignment Station As previously described, electrostatic chuck 202 (engaged to receiver 172 and first robotic transport element 170), engages frame 81 containing substrate 80 at input/output station 120A, and then delivers it to alignment station 130 (see, e. g., FIGS. 7,8,9 and 21).

At alignment station 130, frame 81 is released from electrostatic chuck 202/receiver 172 so that alignment features 52 of frame 81 (see FIG. 20) matingly engage complementary alignment mechanisms (not shown) at the alignment station. Such alignment features may be, for example, pins on frame 81 that are received by holes at alignment station 130. Frame 81 is then re-engaged by the electrostatic chuck and receiver, and, as a result, substrate assembly 82 is now aligned to within the accuracy of robotic transport element 170 (e. i 0.002 inches (0.05 mm)).

In some embodiments, a visco-elastic pad (not shown), such as a foam rubber pad, is included at alignment station 130. When substrate assembly 82 is re-engaged, substrate 80 is pressed against the pad to remove any air pockets that are formed between substrate 80 and electrostatic chuck 202. With substrate 80 pressed against the pad, the substrate-adhering vacuum of the receiver 172 is activated, and powder-attracting electrodes 307 can also be activated to aid in adhering the substrate to electrostatic chuck 202.

Alignment station 130 may improve substrate alignment to the electrostatic chuck, especially when misalignment-causing circumstances are present. One such circumstance arises when a substrate frame (e. g., substrate frame 81 or 91) is stacked on other frames at an input/output substation. It will be appreciated that as frames are successively stacked, the frames may deviate from a properly aligned position. When a robotic transport element (e. g., elements 170 or 180) engages the frame with a clamping feature, such as vacuum cups 1670 (see, FIG. 22), misalignment may occur. Using alignment station 130, alignment accuracy is improved to within the placement accuracy of the robotic transport element (at alignment station 130) so that substrate 80, for example, can be positioned with the requisite accuracy during the deposition operation. Alignment station 130 advantageously provides a secondary benefit whereby the visco-elastic pad facilitates intimate contact between electrostatic chuck

202 and substrate 80.

Second robotic transport element 180 engages frame 91 containing a cover layer 90 and uses alignment station 130, in the manner described above, to confirm localization of frame 91. The second robotic transport element 180 moves cover assembly 92 to lamination support block 1901 (see FIG. 23, frame 91 not shown) and deposits it thereon.

The alignment features described above are suitable for processing substrates in batch or piece-wise fashion, as in the illustrated embodiments. Alignment issues are advantageously addressed in a different manner in the context of continuous processing operations. For example, if, in a continuous process, the substrate is deployed on a tape, then frames can be periodically locked to the tape as it is processed through portions of the present apparatus where alignment issues are particularly important. To provide adjustment capability for such a process, a small amount of loosely fitting tape can be employed between the locked frames, thereby allowing the spacing between the frames to be adjusted based on alignment considerations.

Framing and alignment considerations are described further later in this specification with reference to deposition station 150 and dose measurement station 140, where alignment is particularly important.

Deposition Engine In one embodiment, after substrate assembly 82 is aligned at alignment station 130, first robotic transport element 170 moves the substrate assembly to deposition station 150. In another embodiment, substrate assembly 82 is first moved to dose measurement station 140 so that baseline optical data can be recorded before the powder-deposition operation, and then robotic transport element 170 moves substrate assembly 82 to deposition station 150.

Robotic transport element 170 is rotated 90° to align frame 81 of substrate assembly 82 with deposition opening 158 (see FIG. 7) at deposition station 150. Locating pins 1650 (FIGS. 17 & 22) are used to establish the alignment of receiver 172/electrostatic chuck 202 /substrate assembly 82 with deposition opening 158.

An illustrative deposition engine 800 is illustrated in FIG. 24. Deposition engine 800 includes deposition station 150 and illustrative powder feed apparatus 801. A deposition engine presents the possibility for a variety of processing problems. Such problems include,

for example, powder compaction, non-uniform powder flux, powder loading, operating stability and powder size limitations, among others. In some applications, such problems can be addressed by modifying the powder. The present invention, however, is intended to be useful for applications, such as pharmaceuticals, in which there is often little or no ability to modify powder without raising regulatory issues. As such, the deposition engine itself should be designed to avoid such difficulties. Various components of illustrative deposition engine 800 can improve the deposition operation, resulting in: decreased powder compaction, more uniform powder flux, ease of powder loading, improved operating stability, the ability to use a wide variety of powder particle sizes, and improved powder flow without the powder surface modifications that are often performed in other applications.

Illustrative powder feed apparatus 801 includes auger rotation motor 804, hopper 806, vibrator 808, auger 810, clean gas source 814 feeding modified venturi feeder valve 812, powder charging feed tube 816, powder evacuation tubes 818, powder trap 820, and High Efficiency Particulate Air (HEPA) filter 822, interrelated as shown. Illustrative powder feed apparatus 801 is disposed substantially within enclosure 802, which is depicted in phantom for clarity of illustration.

In operation, auger 810 is rotated, via auger rotation motor 804, to feed powder into venturi feeder valve 812. A rotational rate within the range of about 10 to about 80 rotations per minute is satisfactory for such purpose. Modified venturi feeder valve 812 having a venturi well that delivers powder in a substantially straight path from the auger feed (i. e., hopper 806) to powder charging feed tube 816 was used. Such a modified device avoids powder compaction that may be experienced when powder fall to the bottom of the venturi well in standard arrangements. The venturi well should be accessible, for example, by an unscrewing action, so that it can be periodically vacuumed.

Vibrator 808 is advantageously used to keep the powder free-flowing, with vibration intensity set at a level that does not cause substantial aggregation of the powder. The vibrator is illustrated as acting on the hopper 806, but can likewise be applied to a shaft driving a mechanical powder-moving appliance such as auger 810.

When a flow of gas, such as, for example, nitrogen, from clean gas source 814 is admitted to modified venturi feeder valve 812, powder is pulled from auger 810. Moreover, such gas acts to push the powder through powder charging feed tube 816. A modified venturi suitable for use in the powder feed apparatus 801 is commercially available from

Vaccon Company, Inc. through Air Oil Systems, Mainland, PA, or Berendsen Fluid Power, Rahway, NJ.

In place of a venturi, a gas source can be provided to propel powder through powder charging feed tube 816. In one embodiment, gas source 814 directs gas pressure towards the outlet of a mechanical device that feeds powder. The gas jet can be directed and adjusted to act to deagglomerate powder at that outlet.

For electrostatic deposition, the powder must be charged. In one embodiment, powder charging feed tube 816 is made of a material that imparts, by triboelectric charging, the appropriate charge to the powder as it transits the tube making periodic collisions with the sides thereof. As is known in the art, TEFLONS, a perfluorinated polymer, can be used to impart a positive charge to the powder (where appropriate for the powder material) and Nylon (amide-based polymer) can be used to impart a negative charge. In so charging the powder, the tube builds up charge which can, if not accommodated, discharge by arcing.

Accordingly, a conductive wrap or coating is applied to the exterior of powder charging feed tube 816 and grounded. Tube 816 can be wrapped, for example, with aluminum or copper foil, or coated with a colloidal graphite product such as Aquadagt, available from Acheson Colloids Co. of Port Huron, MI. Alternatively, powder charging feed tube 816 can be coated with a composition comprising graphite or another conductive particle such as copper or aluminum, an adhesive polymer, and a carrier solvent, mixed in amounts that suitably preserves the"tackiness"of the adhesive polymer. An example of such a composition is 246 g trichloroethylene, 30 g polyisobutylene and 22.5 g of graphite powder.

The charge relieved by the grounding procedures outlined above can be monitored to provide a measure of powder flux through powder charging feed tube 816. This data is advantageously sent to processor 401 for analysis. As a result of such analysis, deposition operating parameters can be modified, as appropriate, to maintain an on-specification operation. An illustrative arrangement suitable for providing such monitoring is described below.

In one embodiment, a capacitor is placed in series with powder charging feed tube 816. The capacitor lowers the potential generated by the charges collected in the tube 816.

A 1 ; j. F capacitor will build up 1 V for a 1 pC charge. The other pole of the capacitor is connected to ground. The capacitor acts to bring the potential of the powder charging feed tube 816 closer to ground. An electrometer connected to the capacitor provides an accurate WO 01/73431

measure of collected charge. With powder charged to 50 pC/g, 1 uC corresponds to 20 mg of powder. Powder charging feed tube 816 can be biased. With an applied bias of 500V, noise of 10 pA can be anticipated, creating an uncertainty of 3 nC over 3 minute intervals.

Even with such biasing, such a system provides errors as low as 0.3% on measurement of 20 mg of powder. By controlling the conductivity of the grounding wrap or coating, a potential drop along powder charging feed tube 816 can be established, creating an electric field that favors drawing charged powder through the tube while giving uncharged powder greater opportunity to pick up charge.

Another way to impart charge to the powder is by"induction"charging. One way to implement induction charging is to incorporate an induction-charging region in powder charging feed tube 816. More particularly, at least a portion of powder charging feed tube 816 comprises a material such as a stainless steel, which is biased by one pole from a power supply, with the opposite pole grounded. With an appropriate bias, an electric field is created in the induction-charging region such that powder passing through it picks up a charge. The length of the induction-charging region can be adjusted as required to impart the desired amount of charge to the powder. In one embodiment, induction charging is used in conjunction with the tribocharging features described above.

Powder charging feed tube 816 feeds charged powder into deposition station 150 via nozzle 152. Deposition station 150 is enclosed by enclosure 154, comprising, for example, acrylic panels. Nozzle 152 advantageously includes rotating baffle 153 that increases the uniformity of the powder cloud developed in deposition station 150. Nozzle motor 151 drives rotating baffle 153.

An illustrative nozzle 152 with rotating baffle 153 is shown in more detail in FIGS.

25 (plan view) and 26 (side view). Rotating baffle 153 comprises baffle disk 1552 that is supported by three spaced, radially-extending baffle supports 1551. Baffle disk 1552 includes baffle outlets 1553 through which the powder passes. In the embodiment depicted in FIG. 26, which is drawn approximately to scale, the height BH of rotating baffle 153 is about 0.72 inches (18 mm).

Powder is fed through the nozzle 152 with, for example, a gas that is at a pressure of about 20 psi and fed at a rate of about 2.5 liters per minute. The gas is preferably substantially free of water, oil and other impurities, and is preferably a chemically inert gas such as nitrogen or helium. Baffle 153 is advantageously disposed above the outlet of

powder charging feed tube 816 by an amount in the range of about one-quarter to one-half inch. Moreover, baffle 153 advantageously has a larger diameter or cross-section than the outlet of powder charging feed tube 816. For example, baffle 153 may have a one-half inch diameter cross section when a one-quarter inch diameter powder charging feed tube 816 is used. Baffle 153 should be rotated at a rate within the range of about 5 to about 25 rotations per minute to obtain the desired increase in uniformity of the powder cloud.

Referring again to FIG. 24, substrate assembly 82 and electrostatic chuck 202 (both not shown) abut gasket 159 that frames deposition opening 158. Powder moving towards collection zones CZ of electrostatic chuck 202 pass through control grid 157. Control grid 157 is advantageously disposed a distance dgr, d, for example about one-half to about 1.0 inch, below the collection zones, and is biased at about 500V per one-half inch of distance dE, ; d at the polarity intended for the powder. Control grid 157 thus"collimates"the powder cloud attracting powder having an opposite charge (to the charge on the control grid).

Control grid 157 can be, for example, a series of parallel electrical wires, such as can be formed from"switchbacks"of one wire, or, alternatively, a grid of wires. Spacing between parallel sections of wire is advantageously within the range of about 5 to about 15 The rate of powder cloud flux can be monitored by measuring light attenuation between light emitter 155 (e. g., a laser emitter) and light detector 156. This value can be transmitted to processor 401.

Powder that is not utilized at deposition station 150 are drawn back by a pressure differential through powder evacuation tubes 818 to powder trap 820. FIG. 27 depicts internal detail of an illustrative embodiment of powder trap 820. Powder enters powder trap 820 via trap inlet 2104. Powder trap 820 includes a series of conductive first baffles 2101 interleaved with conductive second baffles 2102. To provide the requisite conductivity, the first and second baffles can be formed of materials such as copper, stainless steel or aluminum baffles, for example. The first and second baffles 2101 and 2102 are affixed to respective first trap electrical conduit 2107 and second trap electrical conduit 2109. First and second trap electrical conduits 2107 and 2109 are affixed to trap body 2103. Trap body 2103 is formed, for example, of acrylic polymer (e. g., plexiglass).

First baffles are biased at, for example, +2000V, via first trap electrical conduit 2107, which is in electrical communication with first electrical inlet 2106. The second baffles are

biased, for example, at-2,000V, via second trap electrical conduit 2109, which is in electrical communication with second electrical inlet 2108. Powder returning from deposition station 150 are collected on oppositely charge baffles. When powder is uncharged, a first collision with one baffle can impart a charge, allowing the powder to be attracted to an oppositely- charged baffle that it encounters downstream. Gas exiting powder trap 820 through powder trap outlet 2105 is delivered to HEPA filter 822 (not shown in FIG. 27, see FIG. 24). HEPA filter 822 is typically 99.97 percent efficient in capturing 0.3 micron powder particles, thereby assuring that no more than a relatively insignificant amount of powder, which powder can be detrimental as bioactive agents (without dosing control), is released into the environment.

At some point, the deposition process must be shutdown. Such shutdown may be dictated, for example, by schedule (e. g., where the amount of powder that is deposited is controlled by the period of operation) or in response to the analysis of feedback data from a charge sensor. Shutdown involves reducing the voltage (or the amplitude in the case of a pulsed voltage profile) directed to powder-attracting electrodes 370, and shutting down powder feed apparatus 801. The amount of voltage reduction required for shutdown will vary as a function of the substrate and powder specifics, as well as the amount of powder applied to the substrate. Generally, such voltage reduction is selected to maintain substrate adherence to electrostatic chuck 202, and powder adherence to substrate 80 without causing substantial further powder accumulation. By way of example, stepping down a 2000V deposition voltage (or voltage amplitude where pulsed voltage is utilized) to 400V should be sufficient to retain powder but not attract additional powder.

It should be appreciated that other arrangements or configurations for deposition station 150, as well as for many of the other elements of powder deposition apparatus 100 described herein, may suitably be used in conjunction with the present invention. For example, a first alternate embodiment of a receiver, an electrostatic chuck, and a nozzle (as included at deposition station 150) is depicted via side view in FIG. 28 and via top view in FIG. 29. In the depicted first alternate embodiment, receiver 572 is configured as a rotatable drum. Similarly configured electrostatic chuck 502 is engaged to receiver 572. As in previous embodiments, substrate 580 abuts electrostatic chuck 502. Axle 501 imparts rotation to receiver 572 and advantageously conveys (e. g., through internal conduits, etc.) vacuum and electrical potential to collection zones (not shown) on electrostatic chuck 502.

In some embodiments, axle 501 is also operable to move receiver 572"up and down" relative to four radially-arranged nozzles 552 (only two of which are depicted in FIG. 28).

Grids 557 limit access by improperly charged powder to the collection zones. Variations in the deposition pattern can be minimized by rotating receiver 572.

It should be understood that various elements of the powder feed apparatus depicted in FIG. 24 may be suitably interchanged or replaced by elements performing equivalent functions. For example, the hopper and auger arrangement depicted in FIG. 24 can be replaced with a rotating drum that temporary stores powder and delivers it to a movable belt.

The movable belt then transports the powder to a means for removing the powder from the belt. An example of such a means is a thin, high velocity, jet of gas that blows the powder into powder charging feed tube 816 (FIG. 24) or a conduit in communication therewith.

Alternatively, the powder feed apparatus may be configured in a substantially different manner from the apparatus 801 depicted in FIG. 24. Two such alternative configurations that are suitable for use in conjunction with the present invention are depicted in FIGS. 30 and 31.

FIG. 30 depicts powder feed apparatus 901, in which hopper 907 directs powder to gear wheel 905 that is driven by motor 903. Gas flow 909 directs powder to deposition station 150. Electrostatic chuck 202, electrically connected to high voltage source HV, is depicted in position at deposition station 150 receiving powder at its collection zones.

FIG. 31 depicts powder feed apparatus 1001 comprising fluidized bed 1003. Gas flow 1009 directs powder to deposition station 150 through four powder charging feed tubes 1016. While four such tubes are depicted in FIG. 31, more tubes, or as few as one tube may suitably be used.

In some embodiments, particularly wherein doses such as about 2 ig to about 100 ig are applied to an area of 3 to 4 mm diameter, a jet mill can be favorably employed to deliver powder. Charge can be introduced to the powder by induction charging by applying a potential to the jet mill itself, such as applying a 1, 800V potential to the jet mill. A jet mill suitable for such service is available from Plastomer Products Division of Coltec Industrial Products Inc. (Newton, PA) under the mark TROSTX Air Impact Pulverizer. That jet mill utilizes directly opposing streams of compressed gas, and is usefully operated at a flow rate of about 2.0 to 2.2 liters per minute.

Dose Measurement Station After completing powder deposition, first robotic transport element 170 moves substrate assembly 82 containing powder-bearing substrate 80 to dose measurement station 140 (see, e. g., FIGS. 7 and 8). Robotic transport element 170 is rotated 90° to align frame 81 with measurement opening 146 (see FIG. 8). Receiver locating pins 1650 (see FIG. 22) are used to align receiver 172 with measurement opening 146 to an accuracy of about 0. 0005 inches (0.013 mm). Such alignment accuracy assures that the dose measurements are taken at the proper locations on substrate 80 (i. e., the locations at which the powder is deposited).

In embodiments that do not use frames, such as frames 81 or 91, or another mechanism for assuring consistency of alignment at the deposition station and the dose- measurement station, the dose-measurement system advantageously includes a mechanism for identifying the positions of the powder depositions. In one embodiment, such a mechanism includes a video camera that collects data and further includes suitable electronics for analyzing the video data to determine the boundaries of the depositions. The video camera can be, for example, a CCD.

Dose measurement station 140 includes an apparatus for measuring the thickness (i. e., the amount) of powder deposited on substrate 80. Either of two (or both) optical measurement methods may be used: diffuse reflection and optical profilometry. Diffuse reflection has been used for many years to characterize powder using light sources that emit in a range that is absorbed by the powder. In conjunction with that technology, a theory was developed for diffuse reflection using non-absorbing radiation. The theory derives a term for the thickness of a powder layer. In spite of such utility, to the applicants'knowledge, no products based thereon have been commercially developed. Applicants have discovered that measurements obtained based on diffuse reflection using non-absorbing radiation provide a strong correlation with the deposited amount of powder in a unit form, at least up to a certain amount. The limiting amount varies with the character of the powder and is believed to correspond to an amount of powder that prevents light penetration into lower layers.

The diffuse reflection method is based on reflecting or scattering a probe light beam, such as a laser beam, off of the powder surface in directions that are not parallel to the specular reflection direction. Such scattered light is generally uniformly distributed. Dose depositions that exhibit this property or behavior are said to be"Lambert Radiators."This behavior ("Lambertian scattering") is an important property for dose weight measurements.

The relation between Lambertian scattering and the optical properties of powder are defined by a scattering model developed by Kubelka and Munk.

As described above, non-absorbing radiation is used to create diffuse reflection.

Typical radiation is the visible red lines provided by common gas and diode lasers such as 632.8,635 and 670 nm. When non-absorbing radiation is used and when the dose deposition has a finite thickness, d, the Kubelka-Munk model gives the following relation: [1]Sd = R/(l-R) where: S is a scattering parameter defined by the properties of the particles of the dose deposition; d is the dose deposition thickness; and R is the measured diffuse reflection for dose material on substrates with minimal specular diffuse reflectance wherein Rubsmte ="0 is assumed.

Expression [l] can be rewritten as: [2]d = (1/S) [R/ (1-R)] where: S is assumed to be a constant for a given particle size distribution.

Thus, the thickness of the dose deposition is directly related to the measured diffuse reflectance. If the dose deposition is a Lambertian radiator, as previously defined, the measurement of R is available.

FIG. 32 depicts, figuratively, the diffuse reflection method for characterizing dry powder. Light from light source 3102, which can be, for example, a low-energy laser, is preferably focused through beam splitter 3104. Light source 3102 can direct a beam toward substrate 80 that is wider than the individual"mounds"of deposited powder since the rest of substrate 80 will not have powder that gives rise to Lambertian scattering. Reference beam detector 3106 assists in determining the quality and intensity of the focused beam.

When light impinges on powder 3114 that is deposited on substrate 80, the powder

scatter light SLHT in all directions. Scattered light SLHT is captured by detector 3108.

Preferably, an array of two or more detectors 3108 are used. Amplifiers (not shown) are advantageously used in conjunction with the detectors. The output from the detector (s) 3108 is then connected to a commercial A/D converter (not shown). The resulting digital signal is scanned, such as by using a computer-controlled scanning mechanism 3110. Scanning mechanism 3110 communicates with processor 401 (not shown in FIG. 32). Processor 401 generates a powder thickness profile and, thus, the dose weight measurements of the depositions.

In one embodiment, the powder can be deposited on a substrate that has a specular surface so that the contribution of the surface of substrate 80 to the diffuse reflected component is kept acceptably low. Moreover, substrate 80 is advantageously absorptive so that the measurement will not be sensitive to diffuse reflections from its back surface or from the surface of receiver 172.

Diffuse reflection in a non-absorbing region provides good accuracy in measuring dose deposition amounts ranging from 50-400ag, or even as high as 750 ig to 1 mg, for a 3 or 7 mm deposition dot, depending on the characteristics of the powder. The diffuse reflection method can detect substantially less than a monolayer of powder. If the deposit is more than a monolayer, the probe light beam must partially penetrate the upper layers so that it can be affected by the reflection off of the lower layers to provide an accurate measurement. There tends, however, to be a practical limit (dependent upon the powder) to deposition thickness for it to exhibit Lambertian characteristics. Diffuse reflection is also a measure of the physical uniformity of the dose deposits at the above-listed ranges.

Optical profilometry is useful for obtaining dose measurements that are above the ranges that can be accurately measured by the diffuse reflection method. FIG. 33 depicts, figuratively, an embodiment of the optical profilometry method. When light, such as laser light, from light source 3202 is delivered to deposited powder 3214, light is deflected at an angle that is indicative of the height of the deposition layer. That height can be readily calculated by triangulation. To improve the coherence of deflected light, such deflected light is received by profilometer lens 3212 before being captured by one or more position sensitive detectors 3208. The output data from detector (s) 3208 is scanned using a scanning mechanism 3210 to generate a profile of the powder surface.

The profilometer can be, for example, a confocal profilometer. In a confocal

profilometer, light is directed to the substrate through a lens system, and returned light passes at least in part through the same lens system, though typically the returned light is reflected to a detection site. A confocal profilometer suitable for use in conjunction with the present invention is available from Keyence (Keyence Corp., Japan, or Keyence Corporation of America, Woodcliff Lake, NJ) as Model LT8105. That model focuses source light through a pinhole, and a similar focusing through a pinhole of the return light helps establish focus.

Applying back-and-forth dithering movement to one of the lenses aids in establishing oscillations in the focus that help identify the optimal focus point.

In one embodiment, a slit is used in place of a pin hole, and a spatially resolvable light detector, such as a charge-coupled device (CCD), is used to simultaneously retrieve data for multiple points along a linear area of substrate 80. There exists a possibility that powder- attracting electrodes 370 or some feature of receiver 172 will create strong reflections that can overwhelm efforts to establish the baseline surface of substrate 80. Since substrate 80 is preferably uniform, such reflections can be normalized. Once material is deposited on substrate 80, or where the substrate is sufficiently opaque, clean reflections are obtainable.

Substrate 80 is advantageously scanned before the deposition operation to increase the accuracy of the post-deposition scans. The beam is scanned across the surface and the height of the surface from a reference location is established by triangulation. The difference in height from the reference before and after deposition is attributable to the dose weight.

For the illustrated embodiments, the difference in height is calculated for each column of collection zones CZ, and for each collection zone CZ. Such values are stored in memory 405, and the differences are displayed as a measure of the dosage amount for each dosage unit. When any of the individual unit dosage amounts are beyond the predetermined amount by the preferred five percent value, those units can be later identified and selectively discarded providing 100 percent inspection with non-destructive testing of the actual amounts of each unit dosage.

Since dry powder is typically a good diffuse reflector, it is also possible to use an optical triangulation system that is optimized for diffuse reflection. To determine the pre- dose surface profile, and to establish the height of the substrate under examination during the post-dose measurement, it is preferred that the surface of substrate 80 is a diffuse reflector.

Moreover, substrate 80 is advantageously absorptive so that reflections off of the back surface of substrate 80 or off of receiver 172 are avoided.

For clarity of illustration, the measurements systems of FIGS. 32 and 33 were depicted with only a single light source 3102/3202. More than one light source can, however, be used in such systems.

In some embodiments, the deposition sites are excited in succession and the powder profile is characterized after each light source excitation through scanning mechanism 3110 or 3210 by moving the scanner, for example, from a first site to a second site and so on until all of the deposition sites are characterized. In other embodiments, more than one deposition site is excited at a time and data is obtained by scanning the sites simultaneously. In such other embodiments, it is desirable to optimize conditions for reducing the interference from nearby sites that are being simultaneously characterized. This can be accomplished by optimizing the spacing between the deposition sites or by alternating the excitations of different sites.

It is desirable that light source 3102/3202 be movable in different directions. An industrial process grade (x, y) stage 142 (see FIG. 8) provides movement in the x and y directions. Light source 3102/3202 can be a solid state laser suitable for industrial applications such as, for example, model LAS-200-635-5 available from LaserMax Inc. of Rochester, NY. The laser is advantageously mounted on detection platform 144 (see FIG. 8).

Detectors 3108/3208 can be any suitable detector, preferably silicon, such as those sold by UDT Sensors, Inc. of Hawthorne, CA. Alternatively, large-area solar cells can also be used.

It is advantageous to incorporate both types of the dose measurement systems (i. e., diffuse reflectance and optical profilometry) into dose measurement station 140. By doing so, accurate dose measurements are not limited to one of either low dose or high dose depositions due to the selection of one or the other of the dose measurement systems. FIG. 34 depicts an arrangement that is operable to provide the two modes of dose measurement using a single light source 3302 and a striated substrate 3380.

Striated substrate 3380, shown attached to electrostatic chuck 202/receiver 172, has surface striations 3381 running in one direction. Such a striated substrate is particularly useful for providing both profile and diffuse reflection measurements. The arrangement of FIG. 34 includes, in addition to light source 3302 and striated substrate 3380, detectors 3308a for diffuse reflection measurement mode and position sensitive detectors 3308bfor profilometry measurement mode, and profilometer lens 3313.

The diffuse reflection measurements are made in a plane that contains the striations,

such as plane P, as depicted in FIG. 35. Profilometry measurements are made by positioning the triangulation system with incident and reflected beams in a plane, such as plane O, that is orthogonal to the striation direction, as depicted in FIG. 36. Striations 3381 thus act like a diffuse surface for the profilometry measurement.

Ideally, striations 3381 do not scatter light in a parallel direction, so that any scattered light is attributable to powder on the surface. For both measurements, the substrate is advantageously dyed so that reflections from the substrate's back surface or from receiver 172 do not interfere with profilometry or diffuse reflection measurements.

FIG. 37 depicts an arrangement for dose measurement using two measurement modes, like the arrangement of FIG. 34. In the arrangement of FIG. 37, however, each measurement mode utilizes its own light source. Illustrative detection array 3400 is disposed on support 3402, which support is disposed on detection platform 144 (not shown in FIG. 37, see FIG. 8). The detection array has a diffuse reflectance system comprising diffuse reflectance light source 3404A and detection zones 3408A-3408F. A profilometry system comprises profilometry lens 3413 that is part of a confocal system so that returned light passes through the same lens. Diffuse reflectance light source 3404A is, for example, offset from a center point of the arrangement where lens 3413 is found. As a result, specular reflections will be centered in an area such as area 3420 away from detector zones 3408A- 3408F. Such detector zones include detectors that are preferably angled and arranged to only accept light from an appropriate direction.

It should be understood that the powder deposited at a collection zone CZ are measured both in area and thickness to provide a volume measure manifesting the amount of powder with a deposit at each collection zone. The above diffuse and profilometer measurements, while described in terms of thickness, are also measured in conjunction with areas that are determined by the scanning beams.

In particular, adjacent measurement beams are closely spaced, for example 1 mm apart, so that the transverse region occupied by a collection zone CZ is also measured and considered in the calculations of the amount of powder present at each deposited location.

The beams are advantageously about 6 microns in diameter. For a deposition zone of about 4-7 mm, each powder"dot"will be scanned with four to seven scans, respectively. Such scans are then used to calculate the amount of dosage at each collection zone CZ. The system stores the calculations for each zone in memory for future selective screening of out-

of-specification pharmaceutical or diagnostic unit dosage forms.

EXAMPLE Polyethylene glycol (PEG) powder in an about 3 mm diameter dot has been deposited onto a Mylar substrate. Diffuse reflectance data was obtained using a laser-based Keyence instrument (Keyence Corporation of America) operating at 670 nm in the "intensity"mode. Data was obtained using different, usually larger, fractions of the diffusely scattered light. The analytical properties of the measurement did not appear to be very sensitive to the fraction of collected light (i. e., the measurement is, in this context, unusually robust and ideal for use as an industrial measurement process).

The data set forth in Table 1 below was obtained using the diffuse reflection method, and is the basis for the plot 3500 depicted in FIG. 38, for the four points of this data set. The first three data points were highly correlated and the least squares fit gave an R value, which is a measure of correlation, of 0.999 (for perfect correlation, R = 1). The fourth data point showed variation and the least squares fit for the data set as a whole gave an R value of 0.98.

Both R values were well within accepted norms for analytical procedures to determine dry powder dose weights.

Table 1, Experimental diffuse reflectance and dose weight data PEG Dose Weight, Calculated R/ (1-R) Micrograms, by Assay 108.6 0. 35 86.6 0.312 50.6 0.254 36.6 0.201 Subsequent measurements showed that a high degree of correlation existed for the diffuse reflection measurements and dose weight for various types of dose samples. Based on such data, the degree of correlation is thought to be closely related to the structure of the dose (i. e., in particular whether the structure exhibits Lambertian characteristics).

Application of a Covering Material After dose measurement, first robotic transport element 170 moves receiver 172 and substrate assembly 82 to lamination station 160. As previously mentioned, a holding signal is applied to electrostatic chuck 202 at collection zones CZ to hold the deposited powder to substrate 80 and the substrate to the electrostatic chuck.

At lamination station 160, substrate assembly 82 (i. e., frame 81 and substrate 80) is deposited on top of cover assembly 92 (i. e., frame 91 and cover layer 90), which assembly 92 is engaged to lamination support block 1901 as depicted in FIG. 39 (frames 81 and 91 not shown; see also FIG. 23). Lamination support block 1901 has dimples 1902 into which the indentations of cover layer 90 fit, and further provides support to allow the cover layer and substrate to be pressed together. Alignment mechanisms on frames 81 and 91 and at lamination station 160 assure that the locations with deposited powder on substrate 80 are matched with the indentations, bubbles, etc. in cover layer 90, as illustrated in FIGS. 23 and 39. After the cover layer and substrate are engaged, the holding signal is withdrawn.

After the first robotic transport element 170 moves away, second robotic transport element 180 moves into place above lamination support block 1901. Second robotic transport element 180 has vacuum cups 1870 (see FIG. 8), bonding head 182, and a pad 1880 that compresses substrate 80 against cover layer 90 before and during the bonding operation.

Once in position, second robotic transport element 180 manipulates bonding head 182 to seal all the depositions between the cover layer and substrate thereby forming the unit forms, whether comprising dosage or diagnostic active ingredients. As will be appreciated by those skilled in the art,"bonding"or lamination can suitably be performed using a variety of methods, including, for example, ultrasonics, thermal techniques, or via adhesives. A suitable ultrasonic bonding head is the 900 M-Series ultrasonic welder available from Branson Ultrasonics Corporation in Danbury, CT.

When welding is completed, second robotic transport element 180 moves to its idle position and the final package of dosage forms is removed for final processing as appropriate.

The illustrated bonding method is useful when one desires to keep the deposited powder free of admixture with other components such as film polymers, though it will be recognized that this can be achieved in other ways. The illustrated lamination process

provides bonds that"ring"the area on which material is deposited, but it will be recognized that more uniform lamination processes are also applicable.

In one embodiment of the invention, placebos are produced by laminating a substrate sans deposit, or on which an inactive substance was dry deposited.

Miscellaneous Considerations Many ancillary features that are useful in conjunction with the present deposition apparatus are described herein with particularity. For instance, very favorable results are obtained using one method of aligning the substrate with the deposition station 150 and with the dose measurement station 140. The illustrated embodiments utilize frames to facilitate such alignment. Those skilled in the art will recognize that many of the features described herein are useful without others that are described, such as a deposition apparatus that does not use frames.

In some embodiments, the electrostatic chuck will be cycled out of the process and reused sooner than in the illustrated embodiments. For example, in embodiments where the substrate is a film that is advanced on rollers, the electrostatic chuck used in deposition can be brought in contact with the film when the film advances to the deposition station, and removed immediately thereafter. If necessary, another chuck can be used to assure that the film is smooth and flat (in most embodiments) when presented to a dose-measurement station. Such an embodiment with a roller-fed film will typically not use frames, though frames are an option as discussed above.

Using the techniques and apparatuses described herein, uniform depositions of 5%, and as precise as +3% of a target amount are obtained. Such depositions can include, for example, depositions onto 4 mm diameter collection zones of amounts ranging from 2 llg to 50 mg.

In view of the low variability in dosage levels (i. e., the amount of active ingredient) of unit dosage forms produced in accordance with the present teachings, such dosage forms, and the methods and apparatus by which they are made, are advantageously used for treating a unique set of disease conditions that require a well-controlled dose regimen. Such well- controlled dose regimens may be required, for example, for compounds with overlapping doses and narrow therapeutic windows. Such narrow therapeutic windows may be necessary to avoid toxic side effects, or due to changes in disease state, or as a function of the

size/metabolism of the patient, or due to changes in the patient's condition. Several examples of narrow-therapeutic-window products are described below.

EXAMPLE I-Levothyroxine Adult doses (micrograms-ug) : 25,50,75,88,100,112,125,137,150,175,200 and 300.

Recommended pediatric doses (g) for Congenital Hypothyroidism: Age Dose/Day Daily Dose/Kg body wt.

0-6mo. 25-50 8-10 6-12 mo. 50-75 6-8 1-5 yr. 75-100 5-6 6-12 yr. 100-150 4-5 EXAMPLE II-Digoxin Adult doses (lAg) : 125,250 and 500.

Patients with renal insufficiency require a smaller than usual maintenance dose of Digoxin.

Digoxin toxicity develops more frequently and lasts longer in patients with renal impairment because of decreased excretion of Digoxin. Newborn infants display considerable variability in their tolerance to Digoxin. Premature and immature infants are particularly sensitive, and dosage must not only be reduced but must be individualized according to their degree of maturity.

EXAMPLE III-Warfarin Adult doses (milligrams-mg): 1, 2,2.5,3,4,5,6,7.5 and 10.

EXAMPLE IV-Nitroglycerin Adult doses (jug) : 300,400 and 600.

Additional Final Dosage Forms As previously noted, unit dosage forms, such as unit forms 6 of FIGS. 1-5, can be used to create a variety of final dosage forms useful for different applications. In one embodiment, a final dosage form is produced by disposing one or more unit dosage forms 6 within an outer shell via well-known"blow-fill-seal"technology, as depicted in FIGS. 43a- 43d.

First, a pharmaceutically-acceptable polymer 4308p is"blown,"such as with compressed gas, into mold 4302 such that polymer 4308p remains against inner wall 4304 of mold 4302. Upon cure, polymer 4308p will form outer shell 4308 of a final dosage form 4310 (see FIG. 43d). Although depicted with a"peanut"shape, it should be understood that mold 4302 can be suitably formed to provide a final dosage form having any one of a multiplicity of desired shapes.

As illustrated in FIG. 43b, one or more unit forms 6, as is required to obtain a desired dosage level, is introduced into mold 4302 after polymer 4308p has cured. After introducing the desired number of unit forms 6, and any additional fillers, etc.,"mouth"4306 of mold 4302 is sealed, as depicted in FIG. 43c. Polymer 4308p, for example, can be used to seal mouth 4306. Mold 4302 is then opened, and final dosage form 4310 is removed, as depicted in FIG. 43d.

In another embodiment, pharmaceutical films (e. g., starch-derived, cellulose-derived, polyethylene glycol-derived, etc.) having sufficient thickness are used as a"container"for one or more unit forms 6. As depicted in FIG. 44a, a first film 4402 receives one or more unit forms 6 in one or more wells 4404. Second film 4406 is placed over first film 4402 to seal the wells 4404, as depicted in FIG. 44b. The films can then be diced to separate the wells 4404 providing a plurality of final dosage forms 4410, as illustrated in FIG. 44c.

In a third embodiment of a final dosage form, a strip 4 is sandwiched between two films 4502 and 4504, as depicted in FIG. 45a. The elements of strip 4 have been previously described (see FIG. 1 and the accompanying description), and include a substrate 8 and a cover layer 9. Substrate 8 includes a plurality of depositions that have been deposited in accordance with the methods, and via the apparatus, described herein. Each deposit includes an active ingredient. The cover layer 9 includes a plurality of bubbles or bumps 12 that are aligned with the deposits on substrate 8. A bubble 12, an"underlying"portion of substrate 8

and an associated deposit define a unit form 6. Strip 4 thus comprises a multiplicity of unit forms 6.

Films 4502 and 4504 are bonded to one another, or to strip 4, thereby sandwiching unit forms 6 therebetween and creating a secondary package therefor. Information pertaining to unit forms, etc., is advantageously printed or otherwise reproduced on the secondary package. The secondary package and included strip 4 can be diced producing a plurality of "postage stamp"final dosage forms 4510, one of which is depicted in FIG. 45b. In embodiments in which the secondary package is edible, dosage form 4510, in its"postage stamp"form, may be ingested. In embodiments in which the secondary package is not edible, unit form 6 must be removed for administering.

In a further embodiment, a final dosage form comprising a plurality of unit forms 6 having the same or different active ingredients and capable of timed release is provided.

Such final dosage forms have segregating layers that separate or segregate each of the unit forms within the final dosage form. Illustrative embodiments of such a final dosage form are depicted in FIGS. 46 and 47.

FIG. 46 depicts four unit forms 6a-6d within final dosage form 4610, shown in an exploded view for clarity of illustration. In a first embodiment, unit forms 6a-6d are identical (i. e., same active ingredient and same amount of said active ingredient). In a second embodiment, unit forms 6a-6d comprise the same active ingredient, but that active ingredient is present in differing amounts. And in a third embodiment, unit forms 6a-6d comprise different active ingredients.

Final dosage form 4610 comprises"overcoat"or"overwrap"films 4604a-4604d that segregate unit forms 6a-6d from one another. In illustrative final dosage form 4610 depicted in FIG. 46, each overwrap film 4604a-4604d comprises respective"dimple"4606a-4606d that facilitates receipt of one of the unit forms 6a-6d. Final dosage form 4610 can be made by layering a desired number of overwrap films (e. g., overwrap films 4604a-4604d), and sandwiching a strip (e. g., strip 4) that contains a plurality of unit forms 6 between adjacent overwrap films. The strips 4 are produced in accordance with the present teachings.

The overwrap films are aligned such that dimples on each overwrap film are aligned with one another. The unit form-containing strips are aligned with the overwrap films such that a unit form from each strip is positioned within a perimeter of a dimple of an adjacent overwrap film. The various overwrap layers and sandwiched strips are"punched"in a single

operation, yielding final dosage form 4610.

Overwrap films 4604a-4604d may be bonded to a base film 4602 before or during the punching operation. Moving from outermost overwrap film 4604d to innermost overwrap film 4604a, the diameter of the dimple decreases such that the dimples"nest"in the manner in which pots in a set of cookware nest one within another. In an additional embodiment (not depicted), a second grouping of nested overwrap dimples and unit forms are disposed on a second side of base film 4602.

In an alternate embodiment, final dosage form 4610 can be manufactured via a multi-step overwrapping operation wherein a first overwrap encapsulates a first unit form, a second overwrap film and a second unit form are then positioned over the first overwrap, etc. building up final dosage form 4610 layer by layer.

FIG. 47 depicts a further embodiment of a final dosage form containing multiple unit forms 6. Like final dosage form 4610, unit forms 6a-6d of final dosage form 4710 of FIG. 47 may be identical to one another, may comprise the same active ingredient but in different quantities, or may comprise different active ingredients.

Final dosage form 4710 can be manufactured by attaching (e. g., bonding, adhering, etc.) a"diffusion barrier" (e. g., 4704a) to a unit form 6a and then sequentially attaching additional unit forms (e. g., 6b-6d) and additional diffusion barriers (e. g., 4704b-4704c), seriatim. As a function of application specifics, in some embodiments, an overcoat 4706 encompasses the collection of unit forms and diffusion barriers. Similarly, in some embodiments, additional overwrap layers or diffusion barriers 4702 and 4708 are attached to the first and last unit form (e. g., unit forms 6a and 6d).

Description of the overwrap layers and diffusion barriers, as well as additional description of the base and cover substrates, are provided in the following section.

Substrates for Specific-Delivery Dosage Forms Utilizing the present methods and apparatus, the same active ingredient can be made as a (1) prompt-release; (2) delayed release; (3) timed release; (4) post-gastric release; or (5) colonic-release unit form by suitable selection of the base and/or cover substrates. In particular, to produce such dosage forms, the same active ingredient is deposited on a

substrate or laminated with a cover layer that has the following respective properties: (1) rapidly water-soluble; (2) slowly water-soluble; (3) insoluble but water-swellable; (4) acid- insoluble but alkaline-soluble; or (5) insoluble but sensitive to degradation by anerobic attack.

Certain generalization can be made concerning desirable properties of the various substrates, overlays and diffusion barriers previously described. Such properties, and candidate materials possessing such properties, are listed and described below.

Substrate As previously described, the substrate serves as a deposition substrate upon which powder is electrostatically deposited. Materials suitable for use as a substrate advantageously possess the following properties: electrically resistive (minimum 5 x 10" ohm/sq. at a relative humidity < 40%) ; strong; dimensionally stable; low moisture uptake; insoluble (where insolubility does not pose a safety issue); optically diffuse and darkly colored; and salable.

Candidate materials for a base substrate possessing the above-listed desirable properties include, without limitation, ethyl cellulose, cellulose acetate phthalate, water- insoluble acrylic copolymers, paper (specialty if oral approval is sought), cross-linked poly (vinyl pyrrolidinone), cross-linked gelatin, and non-woven fabric.

Example A base substrate was produced from an aqueous dispersion of ethyl cellulose (commerically available from FMC Company of Philadelphia, PA. as Aquasol ECD). The film-formation-temperature of the as-supplied ethyl cellulose was undesirably high. Film- formation-temperature can be reduced with additives, such as, for example, a plasticizer. In one embodiment, triacetin is added to the ethyl cellulose in an amount in the range of about 15 to about 40 volume percent, and preferably between 25 and 30 volume percent. Triacetin additive produced coherent, supple films that formed at low temperatures (e. g., 50°-60° C).

Table II lists the electrical properties of such films as a function of relative humidity (RH).

Table II Electrical Properties of Films Producedfrom Ethyl Cellulose Dispersion Plasticized with Triacetin 20% RH 30% RH 40% RH 60% RH Surface Sheet Resistance, <ohm/square> : 1.0 x 1012 7.9 x 10"4. 1 x 10"1. 8 x l0" Volume Resistivity, <ohm-cm> : 1.0 x 1012 7.9 x 10"4. 1 x 10"1. 8 x 10" As previously described, the substrate and cover layer utilized in conjunction with the present invention are bonded to one another to form a unit dosage form. In an embodiment depicted in FIG. 48, substrate 4880 comprises a bi-layer film that includes hydrophobic layer 4882 and hydrophilic layer 4884. Hydrophobic layer 4882 maintains high electrical resistance and mechanical stability under a wide range of conditions (e. g., temperature, humidity, etc.). Hydrophilic layer 4884 swells or becomes"tacky"upon exposure to high humidity. Bi-layer substrate 4880 can be bonded to a cover layer by ultrasonic welding, exposure to high humidity, or directed application (e. g., by ink-jet printing or micropipette) of small droplets of water.

In one embodiment, bi-layer substrate 4880 comprises an ethyl cellulose dispersion ("ECD") plasticized with triacetin as hydrophobic layer 4882 and hydroxypropyl cellulose ("HPC") as hydrophilic layer 4884. Electrical properties of the HPC-ECD base substrate are provided below in Tables III and IV as a function of relative humidity (RH).

Table III Electrical Properties of Multi-Layer Films Comprising HPC Type LFP Cast on ECD Surface Property Tested 20% RH 30% RH 40% RH 60% RH Surf. Sht. Resistance* HPC 1.5x 1012 8. 0x 10"5. 8x 10"l. 4x l0" Surf. Sht. Resistance EPC 3.0 x 1012 1. 7 x 1012 1. 3 x 10l2 3. 2 x 10" Volume Resistivity** HPC 1. 9 x 10"9. 2 x 10'3 7.0 x l0'2 2.4 x 10l2

Table IV Electrical Properties of Multi-Layer Films Comprising HPC Type JFNF Cast on ECD Surface Property Tested 20% RH 30% RH 40% RH 60% RH Surf. Sht. Resistance* HPC 1. 0 x 10'z 4.7 x 10"2. 3 x 10"1. 0 x 10" Surf. Sht. Resistance EPC 2. 6 x 10'2 1 2 x 10'2 6.8 x 10"3. 8 x 10" Volume Resistivity** HPC 1.1 x 10l2 9.5 x 10'2 5.7 x lOl2 2. 2 x 10l2 (*<ohm/square>, **<ohm-cm>) Other candidate materials for hydrophobic layer 4882 that are commercially- available as aqueous dispersions are cellulose acetate phthalate and water-insoluble acrylic copolymers. Additional candidates that are suitable, but require more complex processing include, without limitation, unmodified cellulose, unmodified starch, chitin and other materials previously identified as candidates for the base substrate.

Other candidate materials for hydrophilic layer 4884 that are readily available include hydroxypropylmethyl cellulose, methylcellulose, modified starches, maltodextrins, natural and synthetic gums, poly (vinyl alcohol), poly (vinyl pyrrolidinone), and the like, and hydrogels derived from these and other similar materials.

A method 4900 for forming such a bi-layer film is depicted in FIG. 49. The illustrative method involves two primary operations: casting the hydrophobic layer (step 4910) and casting the hydrophilic layer (step 4920). The hydrophobic layer is cast, for example, by applying a suitable material (e. g., plasticized ethyl cellulose dispersion) on a casting substrate, as depicted in operation 4910a. A smooth, poorly adherent plastic film (e. g., Mylar, stainless steel) is advantageously used as the casting substrate. The applied material is then dried under conditions of controlled temperature and humidity as per operation 4910b. A temperature of 55°C and relative humidity of 35% have been found to be suitable for performing drying operation 4910b. Other conditions of temperature and relative humidity may suitably be used.

The hydrophilic layer is then cast from a solution applied to the hydrophobic film in

operation block 4920a. The applied solution is dried under conditions of controlled temperature and humidity in operation 4920b. A temperature of 28°C and relative humidity of 45% have been found to be suitable for performing drying operation 4920b. Other conditions of temperature and relative humidity may suitably be used.

After the hydrophobic layer and the hydrophilic layer have been cast, the resulting bi-layer film is then removed from the casting substrate in a final operation 4930. Such removal can be effected by peeling the bi-layer film from the casting substrate.

In an alternate embodiment, rather than casting the hydrophobic layer, a commerically-available pre-formed pharmaceutically-approved hydrophobic film may be used. The hydrophilic layer is then cast over the hydrophobic film.

Cover Layer As previously described, the cover layer is used in the electrostatic deposition process to cover the substrate thereby trapping the deposited active ingredient therebetween.

Materials suitable for use as a cover layer advantageously possess the following properties: immediately soluble in all conditions of pH, temperature and the like; deformable to accept a range of doses; and easily dyed for color coding.

Candidate materials for a cover layer possessing the above-listed desirable properties include, without limitation, commerical hydroxypropylmethyl cellulose, methyl cellulose, hydroxypropyl cellulose, poly (vinyl pyrrolidinone), poly (vinyl alcohol), poly (ethylene oxide).

Sample Reservoir Layer Where integrated diagnostic structural unit forms are desired instead of pharmaceutical dosage unit forms, a"spreading layer"or"sample reservoir layer"may be added in lieu of the above-described cover layer. The spreading layer is a porous layer, composed of particles of controlled particle size, which serves to retain and spread a sample of liquid which is to be assayed. For example, the spreading layer functions to trap cells or to retard the mobility of macromolecules such as proteins.

In general, the particles in the spreading layer should be inert and wettable.

Additional properties of the spreading layer may include, for example, the ability to define a known volume of liquid in a known area, which is a function of particle size. In certain

embodiments, the spreading layer provides a white or reflective surface for optical spectroscopy.

Preferred particulate materials for the spreading layer include commercially available latex beads with a diameter of from below I micron to several hundred microns, most preferably from about 40 to about 200 microns. Cellulose acetate or inorganic particulate materials such as barium sulfate also can be used. The distance between particles in the spreading layer should result in average pore sizes of from about 1.5 microns to about 50 microns, most preferably from about 10 to about 30 microns. The void volume in the spreading layer should range between from about 60% to about 90%.

Latex and cellulose acetate are preferred materials for the spreading layer because manufacturers can control the polymerization reaction for these materials and, thus, can control particle size. Control of particle size is important to control the volume of liquid retained, as previously discussed. Moreover, with respect to electrostatic deposition of the spreading layer, particle size influences the degree of charging, deposition and, ultimately, the accuracy and uniformity of coverage. These relationships are well-known to those of skill in the art.

It is preferred that the particles of the spreading layer be deposited in a uniform layer with a thickness of at least a monolayer. The thickness of this layer will be dictated by particle size and by the desired volume capacity. Various geometries of the spreading layer, for example, a concave geometry to form a"cup"for the liquid sample, are also within the scope of the present invention.

Additional materials may be deposited onto, or codeposited with, the spreading layer.

Such additional materials may include surfactants, carriers or binders (for example, polysaccharides), buffering agents, solvents or reagents for detection. Examples of reagents for detection that can be deposited electrostatically include, for example, those utilized in enzyme-coupled reactions, such as alkaline phosphatase.

Diffusion Barrier A diffusion barrier may be used, for example, in final dosage forms containing multiple unit dosages, such as final dosage form 4710. Materials suitable for use as a diffusion barrier advantageously possess the following properties: swollen equally across full pH range; control diffusion of water; cross-linked water-soluble polymer; active

ingredient delivery rate controllable by material thickness or by degree of cross-linking density.

Candidate materials for the diffusion barrier include, without limitation, poly (methacrylic acid), acrylic hydrogels (e. g., mildly cross-linked polymers of hydroxyethyl or hydroxypropyl acrylate or methacrylate), polysaccharides (e. g, starches, agar, maltodextrin, etc.), gums (e. g., acacia, gellan, etc.), and carboxymethyl cellulose.

Overcoat Films An overcoat (overwrap) film is used, for example, where a secondary packaging layer surrounds the unit forms, such as for final dosage forms 4310,4410,4510,4610, and some embodiments of 4710. Properties of the overcoat films are defined as a function of the desired characteristic (e. g. prompt-release; delayed release; post-gastric release, etc.) of the final dosage form.

In particular, for release in the stomach, the overcoat film is advantageously acid soluble. Suitable acid-soluble materials include, without limitation, poly (vinyl pyridine), and amine-substituted acrylic copolymers. For release in the small intestine, the overcoat film is alkaline soluble and/or enzyme erodable. Suitable alkaline-soluble materials include, without limitation, carboxyl-substituted acrylic copolymers and polymeric derivatives of alginic acid. Suitable enzyme-erodable materials include, without limitation, protein (e. g., casein, gluten, albumin, etc.), lipid, starch, polylactide and poly (lactide-co-glycolide).

For colonic release, the overcoat film is advantageously universally but slowly water soluble and digestible by anerobic bacteria. Suitable water-soluble materials include, without limitation, ultra-high molecular weight poly (ethylene oxide), high molecular weight poly (ethylene glycol) s blended with poly (vinyl pyrrolidinone) or poly (vinyl alcohol), shellac, fully (> 98%) or slightly (< 25%) hydrolyzed poly (vinyl alcohol), and poly (styrene-co- maleic anhydride), high molecular weight acrylate and methacrylate copolymers containing significant amounts of acidic monomers such as acrylic acid and methacrylic acid.

Adhesives Adhesives are used, in some embodiments, for bonding the substrate and cover layer together, and for bonding various overcoat/overwrap layers to other layers. For buccal,

gingival and nasal locations, the adhesive advantageously provides good adhesion and is non-toxic. Suitable adhesives include, without limitation, synthetic rubber, acrylic pressure- sensitive adhesives, dental temporary, and maltodextrin. For dermal applications, the adhesive advantageously provides good adhesion and is non-allergenic. A suitable adhesive is the type used for adhesive bandages. For vaginal and rectal applications, the adhesive advantageously exhibits poor adhesion and is non-allergenic. A suitable adhesive is a "swell-in-place"material such as polysaccharide.

All patents and patent applications cited in this specification are incorporated herein by reference in their entirety. Any patent application to which this application claims priority is also incorporated herein by reference in its entirety.

It will be understood by those skilled in the art that variations in the illustrated devices and methods may suitably be used in conjunction with the present invention and that the invention may be practiced otherwise than as specifically described. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the claims that follow.