BARE RETICLE STORAGE CHAMBER AND STOCKER

Technical Field

The present disclosure relates generally to the technical field of automated tools used for integrated circuit fabrication and, more particularly, to automated reticle handling tools .

Background Art Presently, conventional processes for manufacturing integrated circuits ("ICs") include a number of process steps in which a surface of a semiconductor wafer is first coated with a thin layer of a photo-resist material after which the photo-resist material is irradiated with short wavelength light to form a patterned latent image in the photo-resist layer. A subsequent processing step develops the latent image thereby leaving patterned photo-resist material on a wafer's surface. In processing a semiconductor wafer to fabricate ICs, the preceding procedure for establishing patterned photo-resist material on a wafer's surface may be repeated dozens of times. The pattern formed in the photo-resist layer on a wafer's surface generally differs for each of the dozens of photoresist exposures performed during IC fabrication. Thus, fabricating a particular type of IC may require a dozen or more reticles each having a different pattern.

In irradiating photo-resist material, the short wavelength light used in forming the latent image passes first through a reticle before impinging upon the thin layer of photo-resist material. In general, reticles used in IC fabrication are made from a thick, planar, rectangularly- shaped or square-shaped piece of glass or quartz. The reticle is opaque in those areas of the pattern where the reticle blocks the short wavelength light from impinging upon the thin layer of photo-resist material. A reticle's opaque pattern is usually formed by a layer of patterned metal, e.g. chromium, coated on one surface of the piece of glass or quartz forming the reticle.

Because reticles are high precision optical devices, they are comparatively expensive. Presently, individual reticles

can cost $ 10,000.00 to $ 100,000.00 depending upon the size of the smallest feature in the pattern to be formed in the photo-resist layer on the wafer's surface. Consequently, a complete set of reticles for fabricating the most advanced ICs today costs $ 100,000.00 and may reasonably cost as much as $ 1,000,000.00. Correspondingly, photolithographic exposure tools which receive both the reticle and the wafer for exposing the photo-resist layer to short wavelength light is also comparatively expensive costing several million dollars. It is not unusual for a typical IC factory, commonly referred to as a "fab," to have an inventory of 1,000 to 10,000 reticles. It has been reported that photolithographic processing may constitute as much as 35% of an ICs manufacturing cost . A typical fab may include several different models of photolithographic exposure tools from different manufacturers, or different models of photolithographic exposure tools from the same manufacturer. While these differing models of photolithographic exposure tools will all accept the same reticles used in manufacturing a particular type of IC, until recently there existed no standard pod, cassette or holder for carrying the set of reticles so individual reticles may be automatically loaded into and removed from photolithographic exposure tools. That is, individual photolithography equipment manufacturers had independently developed idiosyncratic configurations for holders and cassettes which carry reticles while reticles are loaded into and removed from photolithographic exposure tools. Moreover, photolithographic exposure tools supplied by a single photolithography equipment manufacturer all of which will accept the same reticle holder or cassette can require that masks be loaded in differing orientations. Thus, worldwide presently there are in daily use in IC fabs reticle holders and cassettes having dozens of different, incompatible configurations. Furthermore, even if a reticle holder or cassette can be used with a particular photolithographic exposure tool, the reticle (s) which it carries may have an orientation within the holder or cassette which is incorrect for that particular photolithographic

exposure tool. Consequently, if a set of reticles for manufacturing a particularly type of IC are loaded into a cassette for a particular type of photolithographic exposure tool and that particular photolithographic exposure tool is unavailable while another model of photolithographic exposure tool is available, reticles had to be manually moved from one style of cassette that is incompatible with the available photolithographic exposure tool to another style of cassette that is compatible with the available photolithographic exposure tool.

As is well known to those skilled in the art of IC fabrication, within an IC fab contamination must be reduced as much as practicable, or even eliminated if possible. Consequently any automatic equipment for storing reticles and/or transferring them between cassettes having differing configurations must preserve the cleanliness of the fab, particularly cleanliness of reticles passing through the equipment. For example, to reduce reticle contamination reticles may be stored with their patterned surface facing downward. Similarly, to prevent particles from contaminating reticles' patterned surface, that surface may also be protected by a pellicle which includes a frame secured to the reticle and that has a transparent film stretched across the frame's surface furthest from the patterned surface. Properly designed reticle handling equipment can reduce or eliminate a possible source of contamination associated with manual reticle handling.

United States Patent nos . 4,999,671 and 5,442,163 respectively depict and describe photolithographic exposure tools which includes a comparatively small library for storing a number of reticle cases, each of which encloses a reticle. Both of these patents disclose that their respective photolithographic exposure tools load reticle cases into their library one at a time. These patent also disclose automatically retrieving a reticle case from the library, removing the reticle from its case, transporting the reticle to an exposure station, and subsequently returning the reticle to a reticle case for re-storage back into the tool's library.

For many years, manufacturers of semiconductor processing equipment manufacturers have recognized that deficiencies exist in storing, handling and inventorying reticles in IC fabs . FIG. 6 of published European patent application EP 0 846 983 A2 ("the '983 application") depicts a reticle stocker associated with several photolithographic exposure tools. That FIG. of the '983 application also depicts automated guided vehicles for transferring reticles enclosed within a protective reticle case between the reticle stocker and the photolithographic exposure tools. The '983 application discloses that within the stocker reticles are stored bare, i.e. without any protective covering. United States Patent no. 7,058,627 discloses that reticle stockers come in two varieties, bare reticle stockers and reticle stockers that are capable of storing carriers which contain reticles.

United States Patent no. 6,690,993 B2 ("the '993 patent") depicts and describes a reticle stocker that includes a linear reticle rack having a series of lateral spaces or slots each of which may store a single reticle. Typically, the disclosed reticle rack is assembled by lining up a row of modules and by stacking modules vertically upon each other. Consequently, the number of modules included in the reticle rack both in the vertical direction and in the horizontal direction determines the reticle rack's storage capacity. The disclosed reticle stocker also includes a robot which translates laterally back and forth past the entire length of the reticle storage rack traveling along a set of linear bearing rails located at the bottom of the reticle stocker. A computer controlled, magnetically energizes X-axis linear motor located at the bottom of the stocker energized the robot's lateral translation. The robot includes a vertical column which in addition to translating laterally as part of the robot is also automatically rotatable under computer control about a vertical access typically through three-hundred sixty degrees (360°) and at least through one-hundred eighty degrees (180°) . The robot includes a gripper arm, energized by a Z-axis linear motor, that translates vertically up and down along the vertical column between the top and bottom of the reticle rack. The

gripper arm includes a gripper or end effector that is translatable under computer control away from and towards the robot's vertical column into or out of reticle storage slots by an R-axis linear motor. If required to prevent tilting due to the robot's height, the robot may also include an overhead linear motor for energizing the robot's horizontal translation. Driving the robot's translation both a the top and bottom of the vertical column permits aligning the column precisely. The configuration for the various magnetically energized linear motors avoids any moving contacting parts which might introduce particles into the reticle stocker. When operating automatically under computer control, the robot exchanges reticles between the reticle rack's storage slots and a reticle storage pod located at a pod station that includes a series of pod openers. In one configuration for the reticle stocker, the pod openers are located in front of the reticle rack and separated from the reticle storage slots by the robot's linear bearing rails. In another configuration for the reticle stocker, the pod openers are located at one end of the robot's linear bearing rails. The reticle stocker includes a series of manual access doors that are located on the front side thereof separated from the reticle storage slots by the robot's linear bearing rails. The doors allow manual access to the robot, to the reticle rack, and to reticles in the storage slots for maintenance or if an emergency should occur. Within each module, reticle storage slots are separated from each other laterally by side walls. An air circulation system supplies filtered air that flows throughout the reticle rack. Upon initially entering the reticle rack at the top, filtered air first flows vertically downward past reticle storage slots through the area in which the robot translates laterally back and forth between the reticle rack and the manual access doors. Within each vertical column of reticle storage slots, periodically a horizontal shelf projects outward in front of the reticle storage slots to keep filtered air flowing downward past the robot between the storage slots and the manual access doors and away from stored reticles. Some of the downwardly flowing air exits the reticle stocker at the bottom while the

remainder recirculates upwardly from the bottom of the reticle stocker into a plenum located at the rear of the reticle rack on a side of the storage slots that is opposite to the side thereof that faces the robot and the manual access doors. Air initially moving upwardly within the plenum exits horizontally through filters to flow forward through the reticle storage slots toward the robot and the manual access doors. The '993 patent states that the horizontal air flow of air through the reticle storage slots toward the manual access doors prevents particles from coming to rest on stored reticles and on the reticle rack, while filtered air flowing downward past the robot between the reticle rack and the manual access doors removes particles from the reticle rack. The '993 patent further states that the two orthogonal flows of filtered air keeps stored reticles virtually free of particles. The air circulation system provides positive air pressure within the reticle stocker with one manual access door open thereby preventing contaminants from entering the stocker through an open door . Reticles stored bare in a stocker experience various risks from the surrounding environment. For example, reticles stored in this way are exposed to possible contamination by airborne particles, by particles from other reticles, and particles generated by maintenance and service performed on the stocker. In addition to the risk of particulate contamination, naked reticles are also exposed to possible damage by electrostatic discharge ("ESD") - The likelihood that a reticle stored bare in a stocker will be rendered unusable in some way by damage thereto increases as IC feature size decreases. More recently it has been observed that after a number of deep ultraviolet

( ¹¹ DUV") photolithographic exposures anomalities often appear on reticles. These anomalities have ultimately been traced back to crystalline defects growing on previously clean reticle surfaces, even reticle surfaces protected by pellicles. In an effort to standardize reticle cassettes among the products of various photolithography equipment manufacturers, several years ago the Semiconductor Equipment and Materials International ("SEMI") adopted a standard, i.e. SEMI E100-0302 ,

entitled "Specification for a Reticle SMIF Pod ("RSP") Used to Transport and Store 6 Inch or 230 mm Reticles." The SEMI E100-0302 standard is hereby incorporated by reference as though fully set forth here. As implied by the name of the SEMI standard, the configuration of RSP is an adaptation of a previously existing Standard Mechanical InterFace ("SMIF") pod which is widely used in IC fabs for carrying 8 -inch semiconductor wafers during wafer processing. Subsequently, SEMI adopted two (2) more provisional mechanical specifications RSP150 and MRSP150 for transporting and storing 6 inch reticles, i.e. SEMI Elll-0302 and SEMI E112-0302. SEMI standard Elll-0302 specifies a 150 mm Reticle SMIF Pod ("RSP150") used to transport and store a single 6 inch reticle. SEMI standard E112-0302 specifies a 150 mm Reticle SMIF Pod ("MRSP150") used to transport and store up to six (6) 6 inch reticles. The SEMI Elll-0302 and SEMI E112-0302 provisional mechanical specifications are also hereby incorporated by reference as though fully set forth here .

The anomalous crystalline defects appearing on reticle surfaces mentioned previously and frequently identified as "reticle haze" occurs when a cloudy substance forms as a result of airborne molecular contaminants ("AMC"), e.g. SO ₂ and NH ₃ , reacting with moisture in the reticle environment. It has been found that due to multiple cleanings with strong oxidizers a reticle's inert quartz (SiO ₂ ) becomes chemically modified and contains up to several mono- layers of chemically adsorbed water. The adsorbed water hydrates the quartz and turns it into silicic acid ( [Sio _x (OH) ₄ _ _2x ] _n ) that in its partially dehydrated state is commonly identified as silica gel. The acidic quartz surface of reticles created in this way acts as a chemical sponge, absorbing and storing ammonia (NH ₃ ) and other basic compounds. Similarly, the chromium surface layer on reticle surfaces protected by a pellicle also becomes chemically modified during reticle fabrication and use. One set of conditions required for producing reticle haze is ultraviolet ("UV") light in the presence of water. It has been established that excluding and/or removing water from a

reticle's surface breaks the chain of chemical reactions which produce reticle haze.

One technique for excluding and/or removing water from a reticle's surface is storing each reticle in an individual pod which receives a constant purge of low-humidity gas thereby maintaining an extremely dry and clean environment surrounding the reticle. Purge gases used with this reticle storage pod include dry nitrogen (N ₂ ) and extremely clean dry air ("XCDA") . However, reticle storage pods are relatively expensive with the cumulative cost for only the pods required to populate a stocker that stores thousands of reticles approaching $ 1,000,000.00.

As stated previously, in addition to reticle stockers which store bare reticles, there also exist reticle stockers that store reticles inside storage pods such as those characterized by the SEMI standards identified previously. United States Patent no. 6,848,876 ("the '876 patent") discloses a reticle stocker that stores reticles both bare in vertically oriented reticle slots and/or inside storage pods. Regardless of whether the reticles are stored bare or inside storage pods, the '876 patent discloses that they are stored on horizontal, annularly- shaped trays that are stacked vertically to form a carousel which rotates about a vertically-oriented central axis. Published United States Patent Application no. US 2008/0023417 ("the ' 417 published patent application" ) also discloses storing reticles bare on a carousel's horizontal, annularly- shaped trays above annularly- shaped trays that carry reticle storage pods. The '417 published patent application discloses that the storage pods may either be empty or enclose one or more frequently used reticles. Both the issued patent and the published patent application disclose maintaining the reticle storage pod carrying carousel within a controlled, sealed environment in which air flows generally downward. Both the issued patent and the published patent application also disclose that part of the downwardly flowing air passes first down a plenum located centrally within the carousel and then outward horizontally past either bare reticles or reticle storage pods. Furthermore, analogous to the reticle stocker

disclosed in the '993 patent, both the issued patent and the published patent application disclose that their respective reticle stockers include pod openers used when stored reticles enter or leave the stocker.

Disclosure

An object is to provide an improved bare reticle storage chamber and stocker.

Another object is to provide a bare reticle storage chamber and stocker having fully automated reticle handling.

Another object is to provide a bare reticle storage chamber and stocker that facilitates configuring storage capacity to accommodate differing capacity requirements.

Another object is to provide a modular bare reticle storage chamber and stocker that facilitates integrating peripheral devices thereinto such as inspection modules, ID readers and air cleaning modules .

Another object is to provide a bare reticle storage chamber and stocker that reduces cross -contamination among reticles.

Another object is to provide a bare reticle storage chamber and stocker having isolated storage chambers to reduce chemical and ESD cross contamination.

Another object is to provide a bare reticle storage chamber and stocker which reduces haze growth.

Another object is to provide a bare reticle storage chamber and stocker that accommodates manual reticle retrieval if a hardware or power failure occurs.

Another object is to provide a bare reticle storage chamber and stocker that reduces particle and AMC contamination to other reticles if reticles must be manually retrieved therefrom.

Briefly, a bare reticle storage chamber and stocker in accordance with the present disclosure includes at least one reticle input/output -port pod opener adapted for:

1. automatically accessing contents of a pod present therein, the pod being adapted for enclosing at least one reticle; and

2. maintaining a clean mini -environment around whatever may be present in an accessed pod.

The disclosed bare reticle storage chamber and stocker also includes a reticle transfer area that abuts the pod opener. The reticle transfer area houses a reticle handling robot that includes an end-effector adapted for receiving and retaining at least one reticle. Lastly, the disclosed bare reticle storage chamber and stocker also includes at least one bare reticle storage chamber that abuts the reticle transfer area. Abutting the reticle transfer area, the reticle storage chamber houses :

1. a reticle cabinet having a plurality of reticle storage slots, each reticle storage slot being adapted for receiving at least one bare reticle; and 2. a plenum adjacent to the reticle cabinet adapted for providing a substantially uniform flow of gas about and through the reticle cabinet.

The reticle storage chamber also includes an openable and closeable robot access door located on the bare reticle storage chamber that abuts the reticle transfer area. The robot access door when open provides the end-effector of the reticle handling robot housed within the reticle transfer area with access to at least one of the reticle storage slots that is then juxtaposed with the robot access door. Configured in this way, when the reticle storage slot that is juxtaposed with the open robot access door has a reticle disposed therein the reticle storage chamber and stocker can:

1. move the end-effector of the reticle handling robot into the reticle storage slot to receive the reticle;

2. withdraw the reticle from the reticle storage slot;

3. transport the reticle received on the end-effector to an accessible pod present in the pod opener; and

4. deposit the reticle in to the pod present in the pod opener.

An advantage of the presently disclosed bare reticle storage chamber and stocker is that it subdivides a single large storage vault into multiple small sealed chambers while

allowing dry nitrogen (N ₂ ) or other types of dry inert gas such as XCDA to be effectively distributed among the stored reticles to inhibit haze growth.

These and other features, objects and advantages will be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures.

Brief Description of Drawings FIG. IA is a perspective view mainly of front and right hand sides of an embodiment of a reticle storage chamber and stocker in accordance with the present disclosure best illustrating the stocker 's monitor and control panel and two

(2) SEMI standard pod input/output ports used for transferring reticles into and out of the stocker;

FIG. IB is a perspective view mainly of rear and right hand sides of an alternative embodiment of the reticle storage chamber and stocker in accordance with the present disclosure depicted in FIG. IA best illustrating the stocker 's monitor and control panel and two (2) SEMI standard pod input/output ports used for transferring reticles into and out of the stocker;

FIG. 1C is a perspective view mainly of rear and left hand sides of the embodiment of the reticle storage chamber and stocker in accordance with the present disclosure depicted in FIG. IB best illustrating a pair of immediately adjacent bare reticle storage chambers;

FIG. 2 is a plan view of the embodiment of the reticle storage chamber and stocker in accordance with the present disclosure illustrated in FIGs. IB and 1C; FIG. 3 is a perspective view depicting that side of the bare reticle storage chamber which, in the illustrations of FIGs. 1A-1C, faces either toward the stocker ' s monitor and control panel, or toward the two (2) SEMI standard pod input/output ports; FIG. 4 is a perspective view depicting a reticle cabinet having some reticles stored therein which is included inside the bare reticle storage chamber depicted in FIG. 3;

FIG. 5 is a perspective view depicting a portion of the bare reticle storage chamber depicted in FIG. 3 showing in greater detail a robot access door included therein;

FIG. 6 is a perspective view depicting several reticle support brackets upon which reticles rest when stored in the reticle cabinet depicted in FIG. 4;

FIG. 7 is a perspective view depicting the interior of the bare reticle storage chamber illustrated in FIG. 3 that depicts its reticle storage cabinet, a vertically oriented plenum located adjacent thereto, and a vertically oriented wall that is located adjacent to the plenum,-

FIG. 8 is a perspective view depicting in greater detail the plenum depicted in FIG. 7 that is located immediately adjacent to the reticle storage cabinet; FIG. 9 is a perspective view depicting an elevator mechanism included in the bare reticle storage chamber depicted in FIG. 3 for raising and lowering the reticle storage cabinet, the elevator mechanism being located adjacent to a side of the wall depicted in FIG. 7 opposite to that facing the plenum depicted in FIG. 7;

FIG. 10 is a perspective view depicting an elevator drive included in the bare reticle storage chamber taken along the line 10-10 of FIG. 9;

FIG. 11 is a perspective view depicting a preferred embodiment of a forked end-effector included in the reticle storage chamber and stocker mounted on an arm assembly of a

SCARA arm included in the reticle storage chamber and stocker and having a reticle resting thereon; and

FIG. 12 is a perspective view depicting a bar code reader ("BRC") turntable included in reticle storage chamber and stocker for identifying individual reticles by a reticle ID present thereon, and for properly orienting each reticle.

Best Mode for Carrying Out the Disclosure The perspective views of FIGs. 1A-1C illustrate alternative embodiments of a reticle storage chamber and stocker in accordance with the present disclosure referred to by the general reference character 30. A monitor and control panel

32 that appears in FIGs. IA and IB is located adjacent to a front 34 of the reticle storage chamber and stocker 30. The reticle storage chamber and stocker 30 preferably includes at least two (2) immediately adjacent SMIF pod openers 36, one of which abuts the monitor and control panel 32. The pod openers 36, which provide reticle input/output ports for the reticle storage chamber and stocker 30, may either be a pod opener 36 adapted for receiving 150mm SMIF pods, or a pod opener 36 adapted for receiving 200mm SMIF pods. Whether adapted for receiving 150mm or 200mm SMIF pods, the pod openers 36 are preferably substantially of a type described in United States Patent nos. 5,984,610 and 6,086,323 that are incorporated herein by reference as though fully set forth here. The pod openers 36 provide the reticle storage chamber and stocker 30 with an ergonomic design that permits an operator to deposit SMIF pods onto the pod openers 36 and to remove them therefrom at a fixed height.

As described in greater detail in United States Patent no. 7,318,697, when reticles used for photolithography are outside a photolithographic exposure tool and the reticle storage chamber and stocker 30, they are preferably transported within a sealed environment provided by a SMIF pod. Each pod opener 36 permits automatically accessing contents of a SMIF pod while both maintaining a clean mini -environment around whatever may be present there, and while permitting an automated exchange of reticles with a SMIF pod. United States Patent no. 7,318,697 is incorporated herein by reference as though fully set forth here .

One end of an elongated reticle transfer area 42 of the reticle storage chamber and stocker 30 abuts the monitor and control panel 32 and the pod openers 36, and extends outward to one side of the pod openers 36 away from the monitor and control panel 32. As best illustrated in the plan view of FIG. 2, the reticle transfer area 42 encloses a SCARA arm 44 that is carried on a linear track 46 along which the SCARA arm 44 is moveable longitudinally throughout the length of the reticle transfer area 42. The SCARA arm 44 and the linear track 46 are preferably of the type disclosed in United States Patent no.

6,494,666 ("the '666 patent") that is incorporated herein by- reference as though fully set forth here.

As illustrated in FIGs. IB, 1C and 2, the reticle storage chamber and stocker 30 depicted in those FIGs. also includes a pair of bare reticle storage chambers 52 that are respectively located opposite to the monitor and control panel 32 and the pod openers 36 with respect to the reticle transfer area 42. As explained in greater detail below, each bare reticle storage chamber 52 stores up to one-hundred fifty (150) bare reticles. The embodiment of the reticle storage chamber and stocker 30 depicted in FIGs. IB, 1C and 2 illustrate spaces 54 where four (4) additional bare reticle storage chambers 52 may be added. By adding additional bare reticle storage chambers 52 to the embodiment of the reticle storage chamber and stocker 30 illustrated in FIGs. IB, 1C and 2 in each of the four (4) spaces 54 the total reticle storage capacity of the embodiment of the reticle storage chamber and stocker 30 illustrated in FIGs. IA increases to nine-hundred (900) reticles.

FIG. 3 depicts that side of the bare reticle storage chamber 52 which, in the illustrations of FIGs. 1A-1C, abuts the reticle transfer area 42, and also faces across the reticle transfer area 42 either toward the monitor and control panel 32, or toward the pod openers 36. In the illustration of FIG. 3, the lower portion of the bare reticle storage chamber 52 contains a reticle cabinet 62, illustrated in greater detail in FIG. 4. The reticle cabinet 62 preferably includes one- hundred fifty (150) reticle storage slots 64. The reticle storage slots 64 of each reticle cabinet 62 are organized into three (3) vertical columns 66 each having fifty (50) reticle storage slots 64. As depicted in the upper left hand corner of the reticle cabinet 62 illustrated in FIG. 4, each of the reticle storage slots 64 is adapted for receiving a reticle 68 having a pellicle mounted thereon.

Mounted within the bare reticle storage chamber 52, the reticle cabinet 62 is automatically moveable vertically up and down as indicated by a double headed arrow 72. Vertical movement of the reticle cabinet 62 aligns at least a row of three (3) horizontally adjacent reticle storage slots 64 with

a small, moveable robot access door 74 that is placed at a fixed location in that side of the bare reticle storage chamber 52 which abuts the reticle transfer area 42. The fixed location of the robot access door 74 provides the reticle storage chamber and stocker 30 with an ergonomic design that, if necessitated perhaps by an equipment or power failure, permits an operator's manual removal and/or storage of reticles at fixed height.

Movement of the robot access door 74 , depicted in greater detail in FIG. 5, is energized by a pneumatic cylinder 76 and controlled by a cam mechanism 78. Energizing the pneumatic cylinder 76 in one direction opens the robot access door 74 to provide the SCARA arm 44 with access to exposed reticle storage slots 64. In exposing the reticle storage slots 64, the robot access door 74 moves responsive to control provided by the cam mechanism 78 to first tilt outward away from a door seal 82, and to then move downward thereby revealing reticle storage slots 64 of the reticle cabinet 62. Energizing the pneumatic cylinder 76 in the opposite direction reverses the opening motions in closing the robot access door 74 thereby sealing the reticle cabinet 62 within the bare reticle storage chamber 52 and isolating all reticles 68 stored therein from the reticle transfer area 42.

Stored within the reticle cabinet 62, opposite edges of each reticle 68 rests on a bracket 92, best illustrated in FIG. 6, that is secured to a wall 94 of the reticle cabinet 62. Each edge of each of reticle 68, depicted with dashed lines in FIG. 6, when stored in one of the reticle storage slots 64 rests : 1. between two (2) vertically oriented reticle retaining pins 96 located at opposite ends of each bracket 92 ; and

2. on a pair of intermediate vertically oriented reticle supporting pins 98 that are located between the retaining pins 96.

The retaining pins 96 restrain the reticle 68 stored in a slot 64 from moving horizontally within the slot 64.

FIG. 7 depicts the interior of the bare reticle storage chamber 52 illustrated in FIG. 3 specifically depicting:

1. the reticle cabinet 62 included therein,

2. a vertically-oriented, tapered plenum 102 located adjacent to the reticle cabinet 62 and further from the reticle transfer area 42 than the reticle cabinet 62 ; and

3. a vertically oriented wall 104 adjacent to the tapered plenum 102 and even further from the reticle transfer area 42 than the tapered plenum 102.

The tapered plenum 102 in combination with the wall 104 establish a partition that separates the cleanest area 106 of the bare reticle storage chamber 52 from a less clean area 108 thereof. The less clean area 108 of the bare reticle storage chamber 52 contains all moving and control parts included in an elevator that raises and lowers the reticle cabinet 62. To prevent gas from escaping from the top or bottom of the cleanest area 106, the tapered plenum 102 extends from a ceiling of the cleanest area 106, not illustrated in any of the FIGs., downward to a floor 112 of the cleanest area 106. This configuration for the bare reticle storage chamber 52 permits servicing hardware in the less clean area 108 while preserving cleanliness in the cleanest area 106 that contains the reticle cabinet 62. FIG. 8 depicts in greater detail the tapered plenum 102 that has a cross-sectional shape which is wider at an inlet opening 114 located at the top of the tapered plenum 102, and which tapers to a vertex 116 at the floor 112. Several mesh panels 122a-122c, which respectively have different porosities, form that wall of the tapered plenum 102 which faces the cleanest area 106 and the reticle cabinet 62 located therein. The mesh panel 122a located at the top of the tapered plenum 102 has the smallest pores of the three mesh panels 122a-122c. The mesh panel 122b located at the middle of the tapered plenum 102 has larger pores than those of the mesh panel 122a. Finally, the mesh panel 122c located at the bottom of the tapered plenum 102 has the largest pores of all three mesh panels 122a-122c. Properly configured in this way, gas enters

the bare reticle storage chamber 52 at the inlet opening 114 as indicated by arrows 124, and flows into the cleanest area 106 through the mesh panels 122a- 122c as indicated by arrows 126a-126c. The porosities of the mesh panels 122a- 122c are selected to produce a substantially uniform horizontal flow of gas into the cleanest area 106 from the top of the cleanest area 106 to the bottom thereof. An analytic study of the disclosed tapered plenum 102 having differing porosity mesh panels 122a-122c indicates that the tapered plenum 102 provides a substantially uniform horizontal flow of gas into the cleanest area 106. An illustrative example of the three (3) differing porosities for the mesh panels 122a-122c is:

1. the mesh panel 122a has a porosity of 22.6%; 2. the mesh panel 122b has a porosity of 32.6; and

3. the mesh panel 122c has a porosity of 40.2%. For the preceding porosities, the analytic study indicates that a 25 Pa pressure difference between the tapered plenum 102 and the cleanest area 106 and an air volume of 2000 1 per minute flowing into the inlet opening 114 produces a substantially uniform horizontal flow of gas into the cleanest area 106 at a velocity of 3.145 cm/sec.

The tapered plenum 102 is slightly narrower transversely than the bare reticle storage chamber 52 thereby providing a pair of vertically-oriented, elongated vents, not separately illustrated in any of the FIGs. that extend from the cleanest area 106 past the tapered plenum 102 and the wall 104 to the less clean area 108. Configured in this way, gas from the tapered plenum 102 first enters the cleanest area 106 and then ultimately leaves the bare reticle storage chamber 52 through the less clean area 108 where it enters an exhaust vent of the bare reticle storage chamber 52. A positive gas pressure in the cleanest area 106 in comparison with the gas pressure in the less clean area 108 prevents any particles generated in the less clean area 108 from migrating into the cleanest area 106.

The vertically oriented, elongated vents also provide passages around the wall 104 for two (2) sets of three (3) arms

128, only one set of which appears in FIG. 7. The two (2)

pairs of arms 128, which extend from the less clean area 108 to the cleanest area 106, carry the reticle cabinet 62 and are able to move freely up and down within the vertically-oriented space of the elongated vents. Preferably dry nitrogen (N ₂ ) or other types of dry, inert gas such as XCDA flowing through the bare reticle storage chamber 52 continuously and evenly distributed within the cleanest area 106 by the tapered plenum 102 in combination with the mesh panels 122a- 122c effectively prevents haze from growing on reticles 68 stored in the reticle cabinet 62. This horizontal gas flow not only provides a clean environment for storing the reticles 68, but by continuously washing each reticle 68 stored in the reticle cabinet 62 also removes cloudy substances already deposited on reticle surfaces. The small size of the robot access door 74 minimizes the opening of the cleanest area 106 to the reticle transfer area 42, and, correspondingly, the amount of gas flowing from the cleanest area 106 into the reticle transfer area 42 while the SCARA arm 44 exchanges reticles 68 with reticle storage slots 64 of the reticle cabinet 62. While the SCARA arm 44 access the reticle storage slots 64, gas continuously supplied to the bare reticle storage chamber 52 maintains a positive pressure inside the cleanest area 106 thereby reducing the possibility that gas present in the reticle transfer area 42 may enter the bare reticle storage chamber 52.

FIG. 9 depicts an elevator mechanism 132 located in the less clean area 108 of the bare reticle storage chamber 52 depicted in FIG. 3 for raising and lowering the reticle cabinet 62 thereof. The elevator mechanism 132 includes a pair of vertically-oriented linear bearings 134 which are located adjacent to opposite edges of the wall 104 depicted in FIG. 7 adjacent to a side of the wall 104 which faces away from the tapered plenum 102 also depicted in FIG. 7. Each linear bearing 134 carries one set of three (3) arms 128 which move freely up and down the linear bearing 134. The elevator mechanism 132 also includes a vertically-oriented lead screw 136 which, in the illustration of FIG. 9, connects to the lower arm 128 in each set. As is well known to those skilled in the

relevant art, depending upon the handedness of the lead screw 136 rotation of the lead screw 136 in one direction, e.g. clockwise, moves the reticle cabinet 62 upward while rotation in the opposite direction, e.g. counter-clockwise, moves the reticle cabinet 62 downward.

Rotation of the lead screw 136 either clockwise or counter-clockwise is effected by an elevator drive 142 located near the bottom of the wall 104. As best illustrated in FIG. 10, the elevator drive 142 preferably includes a worm gear 144. The worm gear 144 may be rotated either by an electric motor 146 or by an hand wheel 148. Inclusion of the hand wheel 148 in the elevator drive 142 ensures that if a hardware or power failure should occur critical reticles 68 stored in the reticle cabinet 62 can still be safely retrieved by manually cranking the hand wheel 148 to move the reticle cabinet 62 up and/or down. Manually positioning a horizontal row of reticle storage slots 64 adjacent to the pneumatically controlled robot access door 74 permits an operator to manually retrieve the reticles 68 at an ergonomically convenient height. While the reticle storage chamber and stocker 30 operates automatically, rotation of the worm gear 144 by the electric motor 146 under computer control positions a selected horizontal row of reticle storage slots 64 adjacent to the robot access door 74. Consequently, the elevator drive 142 also includes an electronic motor control 152, that is located beneath the wall 104 and the vertex 116 of the tapered plenum 102 adjacent to the elevator drive 142, for controlling operation of the electric motor 146 responsive to computer commands.

As will be recognized by those skilled in the art, computer control of the vertical positioning of the reticle cabinet 62 provides several advantages. First, computer control of vertical positioning of the reticle cabinet 62 permits indexing the reticle cabinet 62 precisely to any desired vertical position. Precise indexing of the reticle cabinet 62 allows a conventional robot, such as the SCARA arm 44, to exchange reticles 68 with reticle storage slots 64 of the reticle cabinet 62 at the fixed pickup/placement height established by the robot access door 74. Exchanging reticles

68 with reticle storage slots 64 of the reticle cabinet 62 occurs independently of any limitation in the vertical stroke of the SCARA arm 44. Also, the storage capacity of the reticle cabinet 62 is limited only by the height of the bare reticle storage chamber 52 and the reticle cabinet 62, and is independent of the robot's vertical stroke. Furthermore, if the reticle cabinet 62 is held stationary, computer operation permits teaching the robot, such as the SCARA arm 44, to exchange reticles 68 with reticle storage slots 64 of the reticle cabinet 62.

FIG. 11 depicts a preferred embodiment of a forked end-effector 162 included in the reticle storage chamber and stocker 30 that is mounted on an arm assembly 164 of the SCARA arm 44. As described in the '666 patent, the arm assembly 164 is secured to an upper end of an outer tube 166 included in the SCARA arm 44. Vertical movement of the outer tube 166 with respect to a support column included in the SCARA arm 44, not illustrated in FIG. 11, raises or lowers the arm assembly 164 together with the forked end-effector 162 mounted thereon. A distal end 172 of a forearm 174 of the forked end-effector 162, that is secured to a rotary joint 176 located at an end the arm assembly 164, includes a rotary joint 178 which supports a preferably pneumatically actuated reticle gripper 180. As described in the '666 patent, the arm assembly 164 of the SCARA arm 44 is automatically rotatable in a horizontal plane about a vertical axis of the arm assembly 164, while the forearm 174 is rotatable in a horizontal plane about a vertical axis 182 of the rotary joint 176. Similarly, the reticle gripper 180 is automatically rotatable in a horizontal plane about a vertical axis 183 of the rotary joint 178.

As depicted in FIG. 11, the reticle gripper 180 include two (2) forks 184 that extend outward from a box- shaped gripper housing 186. A reticle 68, depicted with dashed lines in FIG. 11, rests on the forks 184 while being moved by the SCARA arm 44. The reticle gripper 180 also includes two (2) gripping arms 192, depicted in FIG. 11 in an open position disengaged from the reticle 68, that extend from the gripper housing 186. Upon energizing a pneumatic cylinder located inside the gripper

housing 186 that is not depicted in FIG. 11, reticle-gripping ends 194 of the gripping arms 192 respectively move along arcuate paths to engage opposite edges of the reticle 68 near an edge thereof which is nearest to the gripper housing 186. By engaging sides of the reticle 68, the gripping arms 192 restrain the reticle 68 from moving laterally across the forks 184.

As depicted in FIG. 11, the reticle gripper 180 also includes a pair of round suction cups 196 that project outward from a face 198 of the reticle gripper 180 that extends laterally between bases of the forks 184. Ends of the suction cups 196 that contact an edge of a reticle 68 are pierced by an orifice having a diameter which is less than the thickness of reticles 68. An adjustable bumper 202 also projects outward from the face 198 between each of the suction cups 196 and the nearest fork 184. The suction cups 196, the face 198 and the bumper 202 are substantially coplanar with a reticle 68 resting on the forks 184. Vacuum applied to the suction cups 196, which project further from the face 198 than the bumpers 202, draws a reticle 68 resting on the forks 184 toward the face 198 to contact the bumpers 202 simultaneously preventing the reticle 68 from moving longitudinally along the forks 184 away from the face 198. When assembling the reticle gripper 180, the bumpers 202 are adjusted toward and away from the face 198 so that a reticle 68 held on the forks 184 by the suction cups 196 will be square with respect to the reticle gripper 180.

Referring back to FIG. 2, the reticle storage chamber and stocker 30 also includes a BCR turntable station 212 that is located between the monitor and control panel 32 and the reticle transfer area 42, and between the forwardmost pod opener 36 and a side service door 213 at the front 34 of the reticle storage chamber and stocker 30 illustrated in FIG. IA. The BCR turntable station 212 permits the reticle storage chamber and stocker 30 to identify individual reticles 68 by a reticle ID present thereon, and to properly orient each reticle 68.

As illustrated in FIG. 12, the BCR turntable station 212 includes a rectangularly- shaped base 214. The base 214 is

supported by a set of four (4) jackscrews 216, only two (2) of which are visible in FIG. 35, that are respectively located along opposite edges thereof and near the corners thereof . A planar, circularly-shaped turntable 218 is supported above the base 214 to be rotatable in a horizontal plane about a vertical axis 222. The turntable 218 is pierced by two access cutouts 224. Four (4) reticle corner supports 226, only three (3) of which are visible in FIG. 12, are secured to and project upward above an upper surface 228 of the turntable 218. As illustrat- ed in FIG. 12, each corner of a reticle 68 respectively rests upon one of the corner supports 226 thereby supporting the reticle 68 horizontally above the upper surface 228 with the reticle's patterned surface facing downward toward the turntable 218. A pair of sensor support brackets 232a and 232b respectively project upward above the upper surface 228 at diametrically opposite sides of the turntable 218 near its rim. A pair of optical transmitters 234a and 234b are secured to the sensor support bracket 232a at differing heights above the upper surface 228. A pair of optical receivers 236a and 236b are correspondingly secured to the sensor support bracket 232b at differing heights above the upper surface 228. Configured in this way, the transmitter-receiver pair 234b, 236b that is located furthest from the upper surface 228 provides a through- beam optical sensor for the presence of a reticle 68. Analogously, the transmitter-receiver pair 234a, 236a that is located closer to the upper surface 228 provides a through-beam optical sensor for the presence of a pellicle secured to the reticle 68. If a reticle 68 rests on the corner supports 226, the glass of the reticle 68 becomes a channel which guides a diverging beam of light emitted by the transmitter 234b past the receiver 236b, i.e. either above or below the receiver 236b. , Conversely, if there is no reticle 68 resting on the corner supports 226, some of the diverging beam of light emitted by the transmitter 234b impinges upon the receiver 236b. If a pellicle depends below the reticle 68 resting on the corner supports 226, the pellicle's frame blocks a beam of

light emitted by the transmitter 234a from impinging upon the receiver 236a.

The BCR turntable station 212 also includes a pedestal 242 which is secured to one side of the base 214 and projects upward higher than a reticle 68 resting on the corner supports 226. A scanner support arm 244 extends outward horizontally from the top of the pedestal 242. An optical scanner 246 is secured to the end of the scanner support arm 244 furthest from the pedestal 242. Disposed in this location, the optical scanner 246 can inspect one edge of the reticle 68 to ascertain if a reticle ID is present therealong. While in the presently preferred embodiment the optical scanner 246 is a bar code scanner, in principle the BCR turntable station 212 is easily adapted to be: 1. part of an optical character recognition device which recognizes numbers and/or alphabetic letters; or

2. a radio frequency identification ("RFID") system. After the SCARA arm 44 deposits a reticle 68 onto the corner supports 226, the BCR turntable station 212 attempts to read an ID present thereon along an edge thereof which is nearest to the pedestal 242. If the optical scanner 246 fails to detect an ID on the reticle 68, then a turntable drive located within the base 214 and not illustrated in any of the FIGs. rotates the turntable 218 carrying the reticle 68 horizontally about the vertical axis 222 through an angle of ninety degrees (90°) . After the reticle 68 has been reoriented, the BCR turntable station 212 attempts to read the ID along a different edge of the reticle 68 again seeking to ascertain if a reticle ID is present therealong. In seeking to locate and read a reticle ID, the BCR turntable station 212 may sequentially interrogate the reticle 68 along as many as all of its four (4) edges seeking to locate and read an ID present therealong. Finding the reticle ID in this way establishes a reference orientation for the reticle 68. Having determined the reference orientation of the reticle 68, the SCARA arm 44 in conjunction with the BCR turntable station 212 can then transfer the reticle 68 from the corner supports 226 to one of

the reticle storage slots 64 in one of the reticle cabinet 62s, or to a SMIF pod present and exposed in one of the pod openers 36 with the reticle 68 being in a specified orientation. The disclosed BCR turntable station 212 permits reading ASML, Nikon and/or Cannon reticle bar codes, and also permits easily- reading reticle IDs for all reticles coming into and leaving the reticle storage chamber and stocker 30.

If as sometimes occurs a reticle 68 lacks a pellicle, then the transmitter-receiver pair 234a, 236a fail to indicate when the reticle's patterned surface faces toward the turntable 218. For the two possible orientations of the reticle 68 on the corner supports 226, viewed from above the reticle ID in one orientation appears as a mirror image of the reticle ID in the other orientation. To address this possibility, the optical scanner 246 is capable of recognizing the reticle ID in either orientations. Then, recognizing the reticle ID for either one or the other of the two mirror images correctly indicates that the reticle's patterned surface faces toward or away from the turntable 218. In this way, using the location of the reticle ID the BCR turntable station 212 automatically determines orientation of a reticle 68, and in conjunction with the SCARA arm 44 controls orientation of a reticle 68 both when stored in the reticle cabinet 62 and when loaded into a SMIF pod.

If for some reason the BCR turntable station 212 is unable to determine an ID for the reticle 68, then operation of the BCR turntable station 212 halts and an alarm sounds requesting operator intervention.

Industrial Applicability The following sequence of operations occurs first when removing a reticle 68 from one location within the reticle storage chamber and stocker 30 before delivering the reticle 68 to another location therein.

1. If the reticle 68 is being removed from a pod present in one of the pod openers 36 or from one of the reticle storage slots 64 of the reticle cabinet

62, appropriately open either the SMIF pod or the robot access door 74.

2. Open the gripping arms 192.

3. Lower or raise the SCARA arm 44 until the forks 184 are a specified distance below the reticle 68.

4. Move the forked end-effector 162 laterally to position the fork 184 beneath the reticle 68 and until the bumpers 202 contact the reticle 68.

5. Lift the reticle 68 above its resting position: a. within a pod present in one of the pod openers

36; b. in one of the reticle storage slots 64 of the reticle cabinet 62; or c. on the corner supports 226 of the BCR turntable station 212.

6. Apply vacuum to the suction cups 196 drawing the reticle 68 against the bumpers 202 thereby securing the reticle 68 on the forks 184.

7. Move the reticle 68 into the reticle transfer area 42.

8. Close the reticle-gripping ends 194 against the sides of the reticle 68 thereby centering the reticle 68 on the forks 184.

9. If the reticle 68 is being removed from a pod present in one of the pod openers 36 or from one of the reticle storage slots 64 of the reticle cabinet 62, appropriately close either the SMIF pod or the robot access door 74.

The following sequence of operations occurs when delivering a reticle 68 resting on the forks 184 to a destination within the reticle storage chamber and stocker 30. 1. If the reticle 68 is being delivered to a pod present in one of the pod openers 36 or from one of the reticle storage slots 64 of the reticle cabinet 62, appropriately open either the SMIF pod or the robot access door 74. 2. Release vacuum from the suction cups 196.

3. Release the reticle-gripping ends 194 from the sides of the reticle 68.

4. Move the forked end-effector 162 carrying the reticle 68 to the delivery destination.

5. Lower the reticle 68 to its resting position: a. within a pod present in one of the pod openers 36; b. in one of the reticle storage slots 64 of the reticle cabinet 62; or c. on the corner supports 226 of the BCR turntable station 212. 6. Continue lowering the SCARA arm 44 until the forks 184 are a specified distance below the reticle 68.

7. Withdraw the forks 184 from the destination leaving the reticle 68 there.

8. If the reticle 68 is being delivered to a pod present in one of the pod openers 36 or to one of the reticle storage slots 64 of the reticle cabinet 62, appropriately close either the SMIF pod or the robot access door 74.

Although the present invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is purely illustrative and is not to be interpreted as limiting. Consequently, without departing from the spirit and scope of the disclosure, various alterations, modifications, and/or alternative applications of the disclo- sure will, no doubt, be suggested to those skilled in the art after having read the preceding disclosure. Accordingly, it is intended that the following claims be interpreted as encompassing all alterations, modifications, or alternative applications as fall within the true spirit and scope of the disclosure.