ISOLATION

CLAIM OF PRIORITY

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 62/624,619, filed on 31 January 2018, and entitled "Electrostatic Chuck (ESC) Pedestal Voltage Isolation," which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The subject matter disclosed herein relates to an electrostatic chuck (ESC) designed to increase a pedestal voltage isolation in a processing tool.

BACKGROUND

[0003] In a typical plasma-based processing system, current pedestals used in an ESC rely only on physical separation to isolate RF and AC signals from a ground plane. Any addition of extra electrodes, which carry high voltages, or gas lines (e.g., a nitrogen (N ₂ ) gas-purge line) reduce the physical separation distances to below specifications for given radio- frequency (RF), alternating current (AC), and/or direct current (DC) voltages. The reduced physical separation distances can cause arcing and other detrimental effects in the ESC.

[0004] The information described in this section is given to provide the skilled artisan a context for the following disclosed subject matter and should not be considered as admitted prior art BRIEF DESCRIPTION OF THE FIGURES

[0005] FIG. 1 shows a simplified example of a plasma-based processing chamber, which can include a substrate support assembly comprising an electrostatic chuck (ESC);

[0006] FIG. 2 shows an example of a three-dimensional (3D) representation illustrating several components of the plasma-based processing system of FIG. 1;

[0007] FIG. 3A shows a cross- sectional view of an example of an electrostatic chuck (ESC) assembly;

[0008] FIG. 3B shows a cross- sectional view of an example of a tube adapter portion of the ESC assembly of FIG. 3A;

[0009] FIG. 3C shows a three-dimensional (3D) representation of a top portion of the tube adapter portion of FIG. 3B;

[00010] FIG. 3D shows a 3D representation of an upper portion of a separator sleeve of the tube adapter portion of FIG. 3B;

[00011] FIG. 3E shows a cross- sectional view of an upper portion of the tube adapter portion of FIG. 3B;

[00012] FIG. 3F shows a cross- sectional view of an upper portion of the tube adapter portion near a sealing O-ring of FIG. 3B;

[00013] FIG. 3F shows a cross- sectional view of a central portion of the tube adapter portion of FIG. 3B;

[00014] FIG. 3G shows a cross- sectional view of a lower portion of the tube adapter portion of FIG. 3B;

[00015] FIG. 4 shows a 3D cross-sectional view of the ESC assembly of FIG. 3A. DETAILED DESCRIPTION

[00016] The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in various ones of the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well known process steps or structures have not been described in detail so as not to obscure the disclosed subject matter.

[00017] An electrostatic chuck (ESC) that supports and secures various types of substrates (e.g., silicon wafers) used in semiconductor processing operations. A pedestal supporting the ESC, and the ESC in general, are shown and discussed in greater detail with reference to FIG. 3A, below. Low-frequency (LF) radio-frequency (RF) power, high-frequency (HF) RF power, AC power, DC power, and gas purge-lines are all supplied to the substrate through a lower portion of the pedestal. As an increasing number of power and/or gas purge-lines are being requited to fit within a confined space within the pedestal, there is a concern that the high voltages employed may arc across to grounded surfaces or induce unwanted signals on neighboring power supply lines.

[00018] For example, RF power may be transmitted from, for example, at least the ESC in a plasma-based processing system. The plasma-based processing system may include a first healing element disposed at a first portion of the ESC and a second heating element disposed at a second portion of the ESC. The plasma-processing system may further include a power supply, such as an alternating current (AC) power supply, for powering the heating elements. AC circuitry supplies power to the heaters of the ESC through the pedestal. As is understood by the skilled artisan, the ESC heaters provide an important control to maintain a temperature profile of the process which ultimately leads to better uniformity and etch- rates on a substrate.

[00019] In a particular example, the ESC pedestal transmits RF, AC, and DC signals to grids that are embedded in a ceramic top plate of the ESC via nickel rods in a stem of the pedestal. These signals pass through a tube adapter portion that serves as an interface between the pedestal and a movable bracket used to raise or lower the substrate while mounted on the ESC. The tube adapter also serves as a ground plane. As disclosed herein, various embodiments of the disclosed subject matter used in the pedestal design use insulative tubes, tube adapters with dielectric-coated interior surfaces, and gaps in various geometries to separate the RF, AC, and DC signals from the ground plane, thereby preventing arcing. The inventive subject matter disclosed herein is described with reference to a plasma-based processing chamber.

[00020] With reference now to FIG. 1, a simplified example of a plasma- based processing chamber is shown. FIG. 1 is shown to include the plasma-based processing chamber 101A in which a showerhead electrode 103 and a substrate-support assembly 107A are disposed. Typically, the substrate-support assembly 107A provides a substantially-isothermal surface and may serve as both a heating element and a heat sink for a substrate 105. The substrate-support assembly 107A may comprise an ESC in which heating elements are included to aid in processing the substrate 105, as described above. As understood by a person of ordinary skill in the art, the substrate 105 may a wafer comprising elemental semiconductors (e.g., silicon or germanium), a wafer comprising compound elements (e.g., gallium arsenide (GaAs) or gallium nitride (GaN)), or variety of other substrate types known in the art (including conductive, semiconductive, and non-conductive substrates).

[00021] In operation, the substrate 105 is loaded through a loading port 109 onto the substrate- support assembly 107A. A gas line 113 supplies one or more process gases to the showerhead electrode 103. In turn, the showerhead electrode 103 delivers the one or more process gases into the plasma-based processing chamber 101 A. A gas source 111 to supply the one or more process gases is coupled to the gas line 113. An RF power source 1.1.5 is coupled to the showerhead electrode 103.

[00022] In operation, the plasma-based processing chamber 101A is evacuated by a vacuum pump 117. RF power is capacitively coupled between the showerhead electrode 103 and a lower electrode (not shown explicitly) contained within or on the substrate-support assembly 107A. The substrate-support assembly 107A is typically supplied with two or more RF frequencies. For example, in various embodiments, the RF frequencies may be selected from at least one frequency at about 1 MHz, 2 MHz, 13.56 MHz, 27 MHz, 60 MHz, and other frequencies as desired. However, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will recognize that a coil required to block or partially block a particular RF frequency can be designed as needed. Therefore, particular frequencies discussed herein are provided merely for ease in understanding. The RF power is used to energize the one or more process gases into a plasma in the space between the substrate 105 and the showerhead electrode 103. As is known in the relevant art, the plasma can assist in depositing various layers (not shown) on the substrate 105. In other applications, the plasma can be used to etch device features into the various layers on the substrate 105. As noted above, the substrate -support assembly 107A may have heaters (not shown) incorporated therein. The person of ordinary skill in the art will recognize that, while the detailed design of the plasma-based processing chamber 101A may vary, RF power is coupled through at least the substrate-support assembly 107A.

[00023] Referring now to FIG. 2, a three-dimensional (3D)

representation illustrating several components of the plasma-based processing system of FIG. 1 is shown. A chamber portion 10 IB of the plasma-based processing chamber lOlA of FIG. 1 is shown to include an RF filter enclosure 201, an alternating current (AC) connector 203, a power cable 205, and an RF power feed cable 207. An uppermost portion 107B of the substrate -support assembly 107A of FIG. 1 is also shown. As noted above, the substrate -support assembly 107 A may be an ESC.

[00024] In various embodiments, the ESC may be a tunable ESC (TESC) capable of a tunable temperature control in two-zones on the uppermost portion 107B ofthe substrate-support assembly 107A The temperature- tuning capability of the ESC may be achieved by implementing two electric heating elements (shown as dashed lines in the substrate- support assembly 107A of FIG. 1) embedded under an uppermost portion of the ESC, proximate to the substrate 105. In the case of a two-zone TESC, one electric healing element is implemented for each of the two zones.

[00025] The electric heating elements may be powered by alternating current (AC) supplied by an AC power supply (not shown in the figures) through the AC connector 203 through the RF filter enclosure 201 and the power cable 205. The RF filter enclosure 201 also contains an RF filter (not shown but known in the art) to prevent or reduce RF power from being delivered to the electric heating elements. The temperature of each of the electric heating elements may be controlled by techniques well- known in the art.

[00026] With concurrent reference to FIGS. 1 and 2, during operation of the plasma-based processing chamber 101 A, RF power is supplied to the substrate-support assembly 107A (ESC) through the RF power feed cable 207 (not shown in FIG. 1), as well as to the showerhead electrode 103, from the RF power source 115. The ESC therefore serves as a lower electrode. Equipotential field lines are set up over the substrate 105 between the substrate 105 and the showerhead electrode 103. During plasma processing, positive ions accelerate across the equipotential field lines to impinge on the surface of the substrate 105, thereby providing the desired etch effect, such as improving etch directionality (the person of ordinary skill in the art will recognize any appropriate modifications needed for film deposition as opposed to etch).

[00027] Inferring now to FIG. 3A, a cross-sectional view of an example of an electrostatic chuck (ESC) assembly 300 is shown. The ESC assembly 300 includes a top plate 301, which supports the substrate 105 as described above, a pedestal 303, and a tube adapter 307. The pedestal 303 and the tube adapter 307 are generally secured together by a bolted flange 305. An O-ring 315, or other type of mechanical gasket or sealing device known in the art, prevents atmospheric pressure (internal to the ESC assembly 300) from being pulled down in pressure by a vacuum

environment (external to the ESC assembly 300).

[00028] The tube portion may be formed from a number of materials known to the skilled artisan, such as various types of metals (e.g., aluminum (Al) and stainless steel (e.g., a 316L alloy) or non-metals capable of withstanding the relatively high temperatures encountered within a plasma-based processing system (e.g., the temperature may be approximately 250 °C). In a specific exemplary embodiment, the tube portion is formed from aluminum with an insulating coating on an inner portion (as shown and described with regard to FIG. 3B, below).

[00029] Within the tube adapter 307, three insulative tubes, 309A, 309B, 309C, are shown through which, for example, RF signal electrodes travel to the top plate 301. The person of ordinary skill in the art will recognize that, based on a particular implementation of an ESC assembly, a larger or smaller number of insulative tubes may be used.

[00030] The insulative tubes 309A, 309B, 309C may be comprised of a number of insulating materials known in the relevant art, such as various types of polymers, provided that the material is chosen to maintain structural integrity in the relatively high temperatures encountered within a plasma-based processing system (e.g., the temperature may be approximately 250 °C). Further, the dielectric material should be chosen to have a dielectric strength that remains substantially consistent over time in the presence of the elevated temperatures and the voltages (described with regard to Table I, below). In a specific exemplary embodiment, the insulative tubes 309A, 309B, 309C are comprised of polyimide (such as Kapton ^® , a polymer of imide monomers). Kapton ^® is available from E. I. du Pont de Nemours and Company, 1007 Market Street, Wilmington, Delaware, USA

[00031] The insulative tubes 309A, 309B, 309C are separated and held in place by lower separator sleeves 313B. These sleeves may be formed from a number of dielectric materials, such as various types of nonconducting ceramics. For example, in a specific exemplary embodiment, the lower separator sleeves 313B are formed from Macor ^® . Macor ^® is a machinable glass-ceramic available from Corning Incorporated, One Riverfront Plaza, Corning New York, USA.

[00032] In a specific exemplary embodiment, the tower separator sleeves 313B are sized such that they are loose enough such that the insulative tubes 309A, 309B, 309C may be readily removed or inserted during routine maintenance or repair operations of the ESC assembly 300.

[00033] The tube adapter 307 also is shown to include AC heater wires 311A, 31 IB and thermal chokes 325A, 325B, 325C. The ESC assembly is also shown to include a number of conductive rods 323A, 323B, 323C configured to carry, for example, high voltage signals.

[00034] In a specific exemplary embodiment, the thermal chokes 325A, 325B, 325C may comprise, for example, gold-plated Inconel (an austenitic, nickel-chromium -based alloy). Components comprising Inconel retain their shape and strength over a wide range of temperatures, whereas other metallic-based components, such as aluminum and steel, may creep or otherwise deform at increased temperatures. [00035] Also, in various embodiments, the number of conductive rods 323A, 323B, 323C may comprise, for example, nickel. The number of conductive rods 323A, 323B, 323C are supported by rod supports 313A, which form a portion of the pedestal 303 that is internal to the stem. In various embodiments, the rod supports 313A may comprise, for example, alumina (AI ₂ O ₃ ).

[00036] The tube adapter 307 also includes at least one gas-purge line (not shown as it is obscured by a center one of the insulative tubes 309B). The tube adapter 307 may also contain other power supply lines. The gas- purge lines may be, for example, brass or stainless steel. However, these materials can be the same as what is currently used on a

contemporaneous ESC device and therefore do not need to be modified or changed in light of the disclosed subject matter. Brass is a non-ferrous material so nearby RF signals will have no effect on the purge-gas line. The at least one gas-purge line may carry a variety of gases such as nitrogen (N _¾ ) or argon (Ar) as noted above.

[00037] Overall, an example of various voltages that may be encountered within the ESC assembly are noted below in Table I.

Table I

[00038] By combining the various voltages shown in Table I, one can arrive at a total working voltage on the ESC as:

[00039] Therefore, to prevent, arcing within the ESC assembly, a clearance specification may be determined by a skilled artisan based on, for example, air at a given relative humidity. In an example based on the example voltages supplied by Table I, a clearance specification to prevent arcing is about 394 V/mm (e.g., approximately 10 Volts/mil, where one mil = 0.001 inches), mixed frequency. Therefore, by knowing the clearance specification, a skilled artisan may also calculate an air gap (shown and described with regard to FIG. 3F, below) as:

2838 V/(394 V/mm) = 7.2 mm (about 284 mils or 0.284 inches)

[00040] Further, by knowing the dielectric strength of various materials, the skilled artisan can determine a minimum thickness required for a material. For example, polyimide has a dielectric strength of about 118 V/mm (approximately 3000 V/mil). In comparison, a hard-anodized coating on aluminum is about 25 V/mm (approximately 640 V/mil). By knowing each of the working voltage and the dielectric strength for a given material or coating, the skilled artisan can determine a minimum thickness for a particular application.

[00041] The skilled artisan will recognize that actual voltages encountered within an ESC assembly may vary depending on a given design requirements. Therefore, Table I should be considered to provide examples of voltages encountered simply to provide a better

understanding of the disclosed subject matter in light of the various embodiments described herein.

[00042] As is also known to the skilled artisan, all thin coated or anodized layers should have broken (e.g., rounded) radii at sharp corners and edges to prevent a very thin or non-covered portion of the underlying material (e.g., various edges and corners of the tube adapter 307) from occurring. Also, the thin coated and anodized layers should be formed so as to prevent or reduce cracks through which arcing could occur.

[00043] Referring now to FIG. 3B, a cross-sectional view of an example of a tube adapter portion 310 of the ESC assembly of FIG. 3A is shown. As described above with reference to FIG. 3A, a dielectric coating 317 may be deposited or otherwise formed on an interior portion of the tube adapter 307. As noted above, the dielectric coating may comprise, for example, a hard-anodization coaling or a polyimide coating. A skilled artisan may also consider the coefficient-of-thermal-expansion (CTE) differences between the tube adapter 307 and the dielectric coating 317 to make a determination whether any flaking or particle shedding may occur as the tube adapter 307 undergoes changes in thermal environment. For example, the CTE for the dielectric coating and the CTE for the material from which the tube adapter 307 is formed can be chosen to be

substantially similar. The CTE number and related calculations are known in the art.

[00044] In various embodiments, an enlarged gap portion 319 may be formed proximate to outboard ones of the conductive rods 323A, 323B, 323C to eliminate arcing by forming, for example, an enlarged air gap. The determination of a clearance specification for a size of the enlarged gap portion 319 is discussed above with reference to FIG. 3A and depends partially on the dielectric-breakdown strength of a material chosen (e.g., air) that is within the enlarged gap portion 319.

[00045] Since the O-ring 315 is being forced outward, due to a higher pressure within the tube adapter 307 than outside the tube adapter 307 (at some level of vacuum during a processing operation), the O-ring 315 is pushed against peripheral (outer) walls of the tube adapter 307 and away from the enlarged gap portion 319. Therefore, an increase in the size of the enlarged gap portion 319 does not lessen the integrity of the seal provided by the O-ring 315. [00046] FIG. 3C shows a three-dimensional (3D) representation of a top portion 320 of the tube adapter portion 310 of FIG. 3B. A cutout portion of the tube adapter 307 shows a dimension of the enlarged gap portion 319 that is increased from a standard diameter within the tube adapter 307. As noted above, the enlarged gap portion 319 is formed proximate to outboard ones of the conductive rods 323A, 323B, 323C to reduce or eliminate (e.g., limit) arcing. Although not explicitly shown, the enlarged gap portion 319 may be supplemented by, or replaced by, insertion of another material having a higher dielectric-breakdown strength than air. Such materials are described herein and are otherwise known in the art.

[00047] FIG. 3D shows a 3D representation of an upper portion 330 of one of the lower separator sleeves 313B of the tube adapter 307 portion of FIG. 3B. A determination of an increase in creepage distance, due to the CTE, when the lower separator sleeve 313B experiences an increase in heat due to the processing environment as discussed above. The increase in creepage distance is indicated by a line 321. The line 321 indicates a creepage distance between the thermal chokes 325A, 325B, 325C and an inner wall of the tube adapter 307 (see, e.g., FIG. 3B). The determination of the increase in creepage distance provides a check on whether a clearance specification is maintained, even when components are heated. Such calculations for a determination of the increase in creepage distance for a given CTE, or CTEs for different materials, are known in the relevant art.

[00048] With reference now to FIG. 3E, a cross-sectional view 340 of an upper portion of the tube adapter portion 310 near a sealing O-ring 315 of FIG. 3B, is shown. The cross-sectional view 340 shows an air gap 331 formed by the enlarged gap portion 319 (see FIG. 3C). In this embodiment, the air gap 331 relies on air as a dielectric (insulator) material. However, the person of ordinary skill in the art will recognize that other dielectric materials may be used. For example, and as described above, an anodized layer formed on inner surfaces of the tube adapter 307 provides a dielectric layer for the dielectric coating 317 (see FIG. 3B). In addition to or in other embodiments, a polyimide or other insulative material may be formed on the inner surfaces of the tube adapter 307. In addition to or in other embodiments, a size of the air gap 331 is increased so as to reduce or eliminate any potential arcing between any of the voltage carrying electrodes (e.g., such as the electrodes contained within outboard ones of the conductive rods 323A, 323B, 323C) and portions of the tube adapter 307 proximate the electrodes and the rod supports 313A

[00049] FIG. 3F shows a cross- sectional view 350 of a central portion of the tube adapter portion 310 of FIG. 3B. As noted above with reference to FIG. 3B, the 0-ri.ng 315 is being forced outward, due to a higher pressure within the tube adapter 307 than outside the tube adapter 307 (at some level of vacuum during a processing operation). Consequently, the O-ring 315 is pushed against peripheral (outer) walls of the tube adapter 307 and away from the enlarged gap portion 319 and away from the space 333 between the rod supports 313A and the O-ring 315. Therefore, an increase in the size of the enlarged gap portion 319 does not lessen the integrity of the seal provided by the O-ring 315 between the atmospheric and vacuum portions of the processing system.

[00050] FIG. 3G shows a cross- sectional view 360 of a lower portion of the tube adapter portion 310 of FIG. 3B. A bellows 335 maintains a pressure differential between an inner portion of the ESC assembly 300, at substantially atmospheric pressure, and an external portion of the ESC assembly 300, at some level of vacuum during processing operations. The cross- sectional view 360 is provided so as to more readily identify, to a skilled artisan, locations of the insulative tubes 309A, 309B, 309C, and the AC heater wires 311A, 311B. Further, the cross- sectional view 360 serves to illustrate that since all changes are made on an interior volume of the ESC assembly 300 (FIG. 3A), especially within the tube adapter 307 (see, e.g., FIG. 3B), the various embodiments disclosed herein may be retrofitted readily into an existing plasma-based processing or other substrate-processing system since all external dimensions and connections from the ESC assembly 300 are maintained. Therefore, no modifications to an existing processing system need to occur.

[00051] As noted herein, the air gap 331 and the insula tive tubes 309A, 309B, 309C insulates the high voltage lines within and proximate to the insulative tubes 309A, 309B, 309C from grounded portions (e.g., grounded portions of the tube adapter 307). Therefore, the insulative tubes 309A, 309B, 309C generally extend down to a point at which arcing between the HV lines and the grounded surfaces (e.g., distal to a lower portion of the tube adapter 307) can no longer occur. This point can be determined based on the calculations provided above with reference to FIG. 3A.

[00052] FIG . 4 shows a 3D cross-sectional view of the ESC assembly of FIG. 3A The bellows 335 allows the ESC assembly 300 (see FIG. 3A) to be movable, thereby moving a mounted substrate 105 (see FIG. 1) relative to a movable bracket portion located below the bellows 335.

[00053] Overall, as shown and described herein, the disclosed subject matter incorporated into the ESC assembly 300 of FIG. 3A may use a variety of embodiments described by the disclosed subject matter to isolate high-voltage electrical signals from the ground plane.

[00054] In specific exemplary embodiments as show described herein, one HV isolation technique uses polyimide tubes (e.g., the insulative tubes 309A, 309B, 309C) to enclose RF signal electrodes allowing isolation of these signals before the connection to their respective insulation wires. The use of polyimide is appropriate for this application as it is a very good insulator and can resist the high temperatures in this location. Another

[00055] Another exemplary embodiment uses a HV isolation technique employing a hard-anodized surface or polyimide coating treatment on the inner surface of the tube adapter 307. The surface treatment (e.g., the dielectric coating 317 of FIG. 3B) provides an overall resistance and separation between the HV electrodes and the ground plane (e.g., the tube adapter 307).

[00056] Another exemplary embodiment uses a HV isolation technique employing one or more cut outs in the upper tube adapter geometry (e.g., the enlarged gap portions 319 of FIG. 3C), which provides further isolation between the HV electrodes (e.g., within outboard ones of the insulative tubes 309A, 309B, 309C) and the ground plane (e.g., the tube adapter 307).

[00057] Moreover, since all changes are made on an interior volume of the ESC assembly 300 (see FIG. 3A), especially within the tube adapter 307, the various embodiments disclosed herein may be readily retrofitted into an existing plasma-based processing or other substrate-processing system since all external dimensions and connections from the ESC assembly 300 are maintained. Therefore, no modifications to an existing processing system need to occur.

[00058] Therefore, the description above includes illustrative examples, devices, systems, and methods that embody the disclosed subject matter. In the description, for purposes of explanation, numerous specific details were set forth in order to provide an understanding of various

embodiments of the disclosed subject matter. It will be evident, however, to those of ordinary skill in the art that various embodiments of the subject matter may be practiced without these specific details. Further, well-known structures, materials, and techniques have not been shown in detail, so as not to obscure the various illustrated embodiments.

[00059] As used herein, the term "or" may be construed in an inclusive or exclusive sense. Further, other embodiments will be understood by a person of ordinary skill in the art upon reading and understanding the disclosure provided. Further, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will readily understand that various combinations of the techniques and examples provided herein may all. be applied in various combinations.

[00060] Although various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As indicated above, each of the various portions may be inter-related and each may be used separately or in combination with other ESC embodiments discussed herein.

[00061] Consequently, many modifications and variations can be made, as will be apparent to the person of ordinary skill in the art upon reading and understanding the disclosure provided herein. Functionally equivalent methods and devices within the scope of the disclosure, in addition to those enumerated herein, will be apparent to the skilled artisan from the foregoing descriptions. Portions and features of some embodiments may be included in, or substituted for, those of others. Such modifications and variations are intended to fall within a scope of the appended claims. Therefore, the present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[00062] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The abstract is submitted with the understanding that it will, not be used to interpret or limit the claims. In addition, in the foregoing Detailed Description, it may be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as limiting the claims. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment