WO1997003222A1

WO1997003222A1 - Cassette support and rotation assembly

Info

Publication number: WO1997003222A1
Application number: PCT/US1996/011501
Authority: WO
Inventors: Frederick T. Rosenquist
Original assignee: Asyst Technologies, Inc.
Priority date: 1995-07-10
Filing date: 1996-07-10
Publication date: 1997-01-30

Abstract

A cassette support and rotation assembly (100) for receiving wafer-carrying cassette (113) through a SMIF port and thereafter orienting the cassette to a desired rotational position with respect to a processing station (103) on or in which the cassette is located. The cassette support and rotation assembly according to embodiments of the invention includes a port door (104) for receiving a SMIF pod door (112) and a wafer-carrying cassette supported on the pod door. The assembly further includes elevator (105) to which the port door is rotationally mounted by means of bearings (124a-c) provided around a lower surface of the port door. In embodiments of the invention, the cassette support and rotation assembly further includes a rotation drive mechanism (132) on a lower surface of the port door for controllably rotating the port door with respect to the elevator so as to align the cassette on the top surface of the port door to the desired rotational orientation.

Description

Cassette Support and Rotation Assembly

The present application is a continuation-in-part of U.S. Patent Application Serial No. 08/500,461, entitled "SMIF Indexer With Rotatable Port Door," filed July 10, 1995, which application is currently pending.

The present application is also a continuation-in-part of U.S. Patent Application Serial No. 08/394,698, entitled "Direct Loadlock Interface," ("The '698 Application") filed February 27, 1995, which application is currently pending.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a transfer apparatus for use with standardized mechanical interface (SMIF) systems for facilitating semiconductor wafer fabrication, and in particular to a platform for supporting a wafer- carrying cassette, which platform is capable of controlled rotation to position the cassette at a desired rotational orientation.

Description of the Related Art

A SMIF system proposed by the Hewlett-Packard Company is disclosed in U.S. Patents Nos. 4,532,970 and 4,534,389. The purpose of a SMIF system is to reduce particle fluxes onto semiconductor wafers during storage and transport of the wafers through the semiconductor fabrication process. This purpose is accomplished, in part, by mechanically ensuring that during storage and transport, the gaseous media (such as air or nitrogen) surrounding the wafers is essentially stationary relative to the wafers and by ensuring that particles from the ambient environment do not enter the immediate wafer environment.

The SMIF system provides a clean environment for articles by using a small volume of particle-free gas which is controlled with respect to motion, gas flow direction and external contaminants. Further details of one proposed system are described in the paper entitled "SMIF: A TECHNOLOGY FOR WAFER CASSETTE TRANSFER IN VLSI MANUFACTURING," by Mihir Parikh and Ulrich Kaempf, Solid State Technology. July 1984, pp. 111- 115.

Systems of the above type are concerned with particle sizes which range from below 0.02 microns (μm) to above 200μm. Particles with these sizes can be very damaging in semiconductor processing because of the small geometries employed in fabricating semiconductor devices. Typical advanced semiconductor processes today employ geometries which are one-half μm and under. Unwanted contamination particles which have geometries measuring greater than O.l m substantially interfere with lμm geometry semiconductor devices. The trend, of course, is to have smaller and smaller semiconductor processing geometries which today in research and development labs approach 0.2μm and below. In the future, geometries will become smaller and smaller and hence smaller and smaller contamination particles become of interest. A SMIF system has three main components: (1) minimum volume, sealed pods used for storing and transporting wafer cassettes; (2) a minienvironment surrounding cassette ports and wafer processing areas of processing stations so that the environments inside the pods and minienvironment (upon being filled with clean air) become miniature clean spaces; and (3) a transfer mechanism to load/unload wafer cassettes and/or wafers from the sealed pods to the processing equipment without contamination of the wafers in the wafer cassette from external environments.

A sealed SMIF pod generally comprises a cover mating with a door located on a bottom or other surface of the pod. The wafers generally are seated within a wafer cassette that rests inside the pod on top of the pod door. In order to transfer a wafer cassette from within the SMIF pod to within a particular processing station, a pod is first placed on an interface port of the processing station. The pod is designed so that the pod door overlies a port door covering the interface port, and the pod cover overlies a port plate surrounding the port door. Once located on the interface port, mechamsms within the interface port release and separate the pod door from the pod cover. Thereafter, the cassette may be lowered into the processing station for processing or wafer transfer.

Wafer cassettes and/or individual semiconductor wafers may be accessed and transferred by a wide variety of transfer mechanisms. One example of a cassette transfer mechanism is a cylindrical body and arm robot, also referred to as a pick and place robot, which comprises a central shaft mounted for rotation and translation along a z-axis concentric with the shaft axis of rotation. The robot further includes a first arm affixed to an upper end of shaft for rotation with the shaft, and a second arm pivotally attached to the opposite end of the first arm. The cylindrical body and arm robot further includes a precision gripping mechanism mounted at the free end of the second arm for gripping and transferring the wafer cassette. Alternatively, the gripping mechanism may comprise an end effector for gripping individual wafers. The robot is controlled by a computer such that the gripping mechanism may be controllably moved about in three-dimensional space to access and transfer a cassette and/or wafer.

A cassette includes walls that envelop a wafer so as to allow removal of the wafer only out of a front portion of the cassette. A consequence of this is that a wafer transfer robot must be positioned substantially in front of the opening of the wafer-carrying cassette in order to transfer semiconductor wafers to or from the cassette.

A cassette is positioned within a SMIF pod in a single, predetermined rotational orientation with respect to the pod door each time the cassette is located within the pod. Similarly, a SMIF pod is positioned on a SMIF port door of a processing station in a single, predetermined rotational orientation with respect to the processing station. Conventionally, this rotational orientation of the cassette with respect to the processing station remains constant for the entire period the cassette is located on or within the station. As illustrated in the schematic representation of Fig. 1, a consequence of this fixed rotational orientation is that there is very little flexibility with respect to where a pick and place robot may be positioned on or within a station in order to allow transfer by the robot of wafers to and from a cassette on or within the station. A pick and place robot 20 will be able to transfer wafers 22 to and from a cassette 24 only when an arm 26 of the robot is capable of orienting itself substantially orthogonal to an opening (along a line 28) of the cassette.

Several conventional semiconductor processes operate by initially positioning a cassette-carrying SMIF pod on a port of a processing station, and thereafter lowering the cassette through the port after the cassette has been separated from the pod. For example, often a cassette is loaded through a port of a processing station onto an indexer, which indexer is provided for determining and/or altering the vertical position of a wafer in a cassette. The Semiconductor Equipment and Materials Intemational ("SEMI") standard for the semiconductor industry with regard to indexers for processing and testing stations requires that an indexer be located at a front of the processing station with an edge of the indexer provided parallel to the front of the equipment. This standard has been set so that a robotic handler may transfer a SMIF pod onto the SMIF port of a processing or testing station without requiring customization of the robotic handler or special mampulation of the SMIF pod. Moreover, processing and testing stations typically include other components in addition to the pick and place robot and indexer, such as for example keyboards, CRTs, and other electronic assemblies. The requirement that the indexer be placed parallel to and at the front of a station, and the space required for additional components, makes it difficult to provide the necessary orientation of the indexer to the pick and place robot as described above in conventional systems. Moreover, if more than one indexer were desired within a single station, the pick and place robot had to be capable of translation so that it may be aligned in front of either indexer, or the indexers had to be angled toward the robot, in noncompliance with the applicable SEMI standard. Another semiconductor process where a cassette is loaded through a SMIF port occurs in a loadlock chamber, which allows a cassette and/or wafers to be transferred from a SMIF pod into high-vacuum semiconductor fabrication processes. An example of such a loadlock chamber is shown in U.S. Patent No. 5,391,035 to Krueger. As shown therein, a cassette is separated from a pod, and loaded through a port into a chamber, which chamber is thereafter sealed and evacuated. Thereafter, wafers may be transferred from the chamber to high-vacuum fabrication processes through ports provided within the chamber. It would be advantageous to provide a system allowing the rotational orientation of a cassette within a loadlock chamber to be controllably varied, so that the opening of the cassette may be aligned with ports around the periphery of the chamber. In this way, one loadlock chamber may allow access to several fabrication processes circumferencially located around the loadlock chamber.

SUMMARY OF THE INVENTION It is therefore an advantage of the present invention to provide a cassette support and rotation assembly capable of receiving a cassette through a port and thereafter rotating the cassette to a desired rotational position.

It is another advantage of the present invention to provide a cassette support and rotation assembly as part of an indexer so as to align an opening of a cassette located on the cassette support and rotation assembly with a robotic transfer system. It is a further advantage of the present invention to increase flexibility with respect to the location of an indexer and mechanical transfer system within semiconductor fabrication and test equipment.

It is a still further advantage of the present invention to provide a cassette support and rotation assembly within a loadlock chamber to rotationally align an opening of a wafer cassette seated on the cassette support and rotation assembly with a plurality of ports provided around the periphery of the loadlock chamber.

These and other objects are accomplished by the present invention which relates to a cassette support and rotation assembly for receiving a wafer- carrying cassette through a SMIF port and thereafter orienting the cassette to a desired rotational position with respect to a processing station on or in which the cassette is located. The cassette support and rotation assembly according to embodiments of the present invention includes a port door for receiving a SMIF pod door and a wafer-carrying cassette supported on the pod door. The assembly further includes an elevator to which the port door is rotationally mounted by means of bearings provided around a lower surface of the port door. In one embodiment of the invention, the support and rotation assembly further includes a rotation drive mechanism on a lower surface of the port door for controllably rotating the port door with respect to the elevator so as to align the cassette on the top surface of the port door to the desired rotational orientation.

In operation, a SMIF pod containing the wafer-carrying cassette is loaded on top of a processing station in a predetermined, repeatable and fixed rotational orientation with respect to the port door. After the pod door and the pod top are separated, the port door, the pod door and the wafer-carrying cassette are lowered through the SMUF port. Thereafter, the rotation system on the port door rotates the pod door and wafer cassette in a predetermined manner so as to align the wafer cassette to a pick and place robot or as otherwise desired.

BRIEF DESCRIPΗON OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a top view of a conventional orientation required between an indexer having a wafer-carrying cassette thereon and a pick and place robot; FIGURE 2 is a perspective view of an indexer according to the present invention with the port door lying substantially coplanar with the support plate;

FIGURE 3 is a front view of an indexer according to the present invention with a SMIF pod loaded thereon;

FIGURE 4 is a front view of an indexer according to the present invention with a pod door and wafer-carrying cassette separated from a pod top;

FIGURE 5 is a front view of an indexer according to the present invention showing the port door, pod door, and wafer-carrying cassette rotated with respect to the view in Fig. 4;

FIGURE 6A is a top view of an elevator according to the present invention;

FIGURE 6B is a cross-sectional view through line 6-6 on Fig. 6A;

FIGURE 7 is a partially sectioned front view of an indexer showing a port door rotatably supported on an elevator;

FIGURE 8 is a bottom view of a port door including a rotation drive mechanism according to the present invention;

FIGURES 9, 10 and 13 are bottom views of alternative embodiments of the rotation drive mechanism according to the present invention;

FIGURE 11 is a semiconductor fabrication or test station including an indexer according to the present invention;

FIGURE 12 is a semiconductor fabrication or test station showing a plurality of indexers according to the present invention; FIGURE 14 is a side view of a loadlock chamber including a cassette support and rotation assembly; FIGURE 15 is an alternative embodiment of the cassette support and rotation assembly shown in Fig. 14; and

FIGURE 16 is an alternative embodiment of the present invention showing an eccentric rotation of a port door with respect to an elevator.

DETAILED DESCRIPΗON

The invention will now be described with reference to Figs. 2-16, which relate to a cassette support and rotation assembly for receiving a cassette through a SMIF port and thereafter rotating the cassette to a desired rotational orientation. Although embodiments of the cassette support and rotation assembly are described hereinafter as part of an indexer and a loadlock chamber, it is understood that the present invention may be utilized in a variety of semiconductor fabrication or testing processes where a cassette is received through a port onto a support platform. Moreover, although the invention is described herein with respect to SMIF systems, it is understood that the present invention may operate with any of several wafer storage and transport devices. Additionally, as explained in greater detail below, the present invention may operate without a pod, so that a wafer-carrying cassette is loaded directly onto the cassette support and rotation assembly. The term "semiconductor wafer" as used herein refers to a wafer substrate as it may exist in any of the various stages of the semiconductor wafer fabrication process. Furthermore, it is not critical to the present invention that the wafer cassette include semiconductor wafers. It is contemplated that other substrates may be provided within the cassette, which may then be rotated according to the principles of the present invention as explained hereinafter. Referring now to Figs. 2-5 and 12, there is shown an embodiment of the present invention used within an indexer 100. As described in the Background of the Invention section, the indexer 100 would be located within a semiconductor processing or testing station 103 (Fig. 12) at the front of the station with an edge 101 of the indexer substantially aligned with a front of the station. The indexer in one embodiment of the invention includes a port plate 102, a cassette support and rotation assembly 105, support columns 108, and a base 109. For an indexer sized to accept a 300mm SMIF pod 110, the height, width and depth of the indexer are approximately 16.5 inches, 17.5 inches, and 18.2 inches, respectively. However, it is understood that the dimensions of the indexer 100 may vary in alternative embodiments. Moreover, the indexer 100 may be sized differently when configured to accept SMIF pods other than those housing 300mm semiconductor wafers.

The SMEF pod 110 may be located on top of the indexer 100 either manually or by an automated transport system. The pod 110 includes a pod door 112 and pod top 114. The pod door and top together define a sealed environment in which a cassette 113 carrying a plurality of wafers 115 may be stored and transported. As used herein, the term "cassette" refers to any structure for holding one or more substrates, which structure includes an open end through which the substrates may be inserted and extracted. Properly positioned, the pod 110 is supported on the port plate 102, with the pod door

112 supported on a port door 104 of the cassette support and rotation assembly. The port door 104 and pod door 112 may include a plurality of protrusions 116 received within holes (not shown) on the bottom of the pod door and cassette, respectively, for ensuring that the SMIF pod 110 and wafer-carrying cassette

113 are always positioned in the same, predetermined rotational orientation on the port door. It is understood that other structures may be used to properly align the cassette within the SMIF pod, and the SMIF pod on top of the indexer. For example, 200mm wafer cassettes conventionally include an H-bar construction on the bottom of the cassette for aligning the cassette within the pod. Moreover, it is known to employ kinematic mounts for positioning a cassette with respect to a pod, and a pod with respect to a support surface.

As described in the Background of the Invention section, once positioned on the port plate and the port door, the pod door is separated from the pod top by means of a latch mechanism provided within the port door. Although not critical to the present invention, details relating to such a latch mechamsm are described in U.S. Patent No. 4,995,430, entitled "Sealable Transportable Container Having Improved Latch Mechamsm", which application is assigned to the owner of the present application and is incorporated by reference in its entirety herein. Once the pod door and cover are separated, the port door 104 of the cassette support and rotation assembly 105 may lower the cassette 113 and the pod door away from the port plate 102 and pod cover 114.

The cassette support and rotation assembly, described in greater detail below, includes an elevator 106 (shown by itself in Fig. 6) on which the port door 104 is rotatably supported. In one embodiment of the invention, the elevator 106 includes a central opening to which a portion of the assembly 105 is affixed as described in greater detail below. The elevator further includes ends 118 threaded around a pair of lead screws 120 (Figs. 2 and 7). As shown on Fig. 2, lead screws 120 have ends which are mounted in the port plate 102 and base 109, respectively, and are preferably embedded within the support columns 108 to minimize contaminants in the area of the wafers.

The lead screws may be rotated by a motor (not shown) below or within base 109 to raise or lower the elevator 106 and port door 104 supported thereon, depending on the direction of rotation of the lead screws. As seen in Figs. 4 and 5, after the pod door 112 is separated from the pod top 114, the port door 104 with the pod door and wafer-carrying cassette supported thereon is lowered by the elevator 106 away from the pod top 114. As would be appreciated by those skilled in the art, more or less than two lead screws may be used to raise and lower the elevator 106. The elevator is provided to rotatably support the port door as the elevator is moved upwards or downwards. It will be appreciated that the elevator shown in Fig. 6 may take on other forms and still accomplish its function. For example, the central opening may be omitted, and instead the elevator may include a raised central portion capable of mating with the bearings to thereby rotatably support the port door.

It is further understood that conventional elevation structures may be substituted for the lead screws to raise and lower the elevator 106. For example, the elevator 106 may be affixed to a translating telescopic shaft, such as for example shown in U.S. Patent Application Serial No. 08/394,698, entitled "Direct Loadlock Interface," ("The '698 Application") filed February 27, 1995, which application is incorporated herein by reference in its entirety. The '698 Application discloses a loadlock chamber including a telescopic shaft mounted through the floor of the chamber (such as for example shown in Fig. 4 of the '698 Application). In the context of the present invention, a telescopic shaft may be used with an indexer, loadlock chamber, or any other application for raising and lowering the elevator 106 and the cassette support and rotation assembly 105. A telescopic shaft 115 for use in conjunction with the present invention is shown in Fig. 14 within a loadlock chamber 220 as described in greater detail below. A motor or similar device (not shown), located below the base or chamber raises and lowers the telescopic shaft to the desired elevation. For applications where the shaft operates in an evacuated chamber, a conventional accordion-type bellows 117 may be provided around the telescopic shaft to provide a vacuum seal between the opening in the bottom of the chamber for the shaft and the interior of the chamber.

According to embodiments of the present invention, as shown in Figs. 7-8, the cassette support and rotation assembly 105 includes the port door 104, the elevator 106, support bearings 124a, 124b, and 124c, and rotation drive mechanism 132. The port door 104 is rotatably supported on elevator 106 by means of support bearings 124a, 124b, and 124c. The support bearings 124a-c are rotatably mounted on shafts 126a-c, respectively, which shafts are mounted in the underside of port door 104. Each support bearing 124a-c includes a V-shaped groove 128 which mates with an angled extension 130 around the inner circumference of the elevator 106. One of the support bearings 124a-c may be adjustable so as to initially allow the support bearings 124a-c to be fitted onto the angled extension 130, and also to ensure a tight tolerance between the support bearings 124a-c and the angled extension 130. The support bearings 124a-c and the angled extension 130 cooperate to rotatably support port door 104 with respect to elevator 106 to allow planar and concentric rotation of the port door, while preventing movement of the port door in the x, y, or z directions with respect to elevator 106. While the above- described system for rotatably supporting the port door 104 with respect to the elevator 106 is advantageous for its high degree of dimensional control, as would be appreciated by those skilled in the art, other known systems may be used to rotatably support port door 104 on elevator 106.

Fig. 8 is a bottom view of the port door 104 showing a prefeπed embodiment of the rotation drive mechanism 132 for rotating the port door through a precise and predetermined angle with respect to its position when the wafer-carrying cassette 113 is initially loaded thereon. In a prefeπed embodiment, rotation drive mechanism 132 includes a rotation motor 134 mounted to a bottom surface of port door 104 for rotating a drive gear 136 affixed to an end of the motor 134. Rotation motor 134 may be a conventional motor, such as a stepper or a servo motor with position and/or velocity feedback. The drive gear 136, in turn, meshes with and drives a worm gear 138 rotatably mounted on a bottom surface of port door 104. In this embodiment, a spur gear 139 is affixed on and concentric with the worm gear 138. The spur gear 139 in turn meshes with a circular rack gear 141 fixedly mounted around the periphery of the elevator 106. Although only a small segment of the rack gear 141 is shown on Fig. 8, the rack gear 141 extends 360° around the periphery of the elevator in a prefeπed embodiment. In the embodiment shown in Fig. 8, the rotation drive mechamsm 132 is capable of rotating port door 104 through a full 360°, and the direction of rotation of port door 104 may be reversed by reversing the current flow to rotation motor 134. In this embodiment, the CPU 146 may control the rotation drive mechamsm to orient the port door at any desired angle with respect to the elevator.

The angle of rotation of the port door 104 caused by the rotation drive mechanism 132 will be set by how much the wafer-carrying cassette 113 needs to be rotated in order to properly align the opening of the cassette with the pick and place robot 122. This predetermined angle will vary depending on the position of the indexer 100 relative to the pick and place robot 122 in a particular station configuration.

Rotation motor 134 may be electrically coupled to a central processing unit (CPU) 146 shown schematically in Fig. 8. CPU 146 may also control the rotation of the lead screws 120, or the translation of the telescopic shaft in an alternative embodiment. The rotation drive mechanism 132 shown in Fig. 8 provides an advantage in that it may be controlled by CPU 146 to rotate port door 104 to a precise and highly repeatable predetermined angle, and is capable of ma taining port door 104 at the predetermined angle despite significant external shocks that may impact on the port door. A conventional encoder (not shown) may also be located on the port door 104 and a sensor provided on the elevator, which encoder and sensor together provide closed- loop servo signals to the CPU 146 to further ensure precise alignment of the port door 104 at the predetermined angle. The present invention may additionally include a sensor system (not shown) comprising an emitter and receiver provided respectively on the port door and pick and place robot, which sensor system generates a signal to cease rotation when the cassette opening and robot are properly aligned. Such a sensor system may for example comprise a conventional block-the-beam sensor. The cassette support and rotation assembly may affect rotation of the port door before, during or after the port door is lowered with respect to the port plate 102. It is understood that other known rotating assemblies may be employed to rotate port door 104 with respect to elevator 106. For example, in an alternative embodiment of the invention shown in Fig. 9, the rotation drive mechanism 132 may comprise a motor 134 and drive gear 136 and worm gear 138 as described above, and also a rotation link 140. The link 140 has a first end mounted by a pin 142 to an outer circumference of the worm gear and a second end mounted by a pin 144 to a bottom surface of the elevator 106.

As would be appreciated by those skilled in the art, worm gear 138 cooperates with rotation link 140 such that rotation of worm gear 138 will cause reciprocating rotation between port door 104 and elevator 106. By way of example, the position of the port door 104, worm gear 138 and rotation link 140 shown in Fig. 9 may represent the initial position of the port door when the cassette is first located thereon (such as in Fig. 4). From that position, a 180° rotation of the worm gear 138 will cause the port door 104 and wafer-carrying cassette 113 to rotate from their initial positions to a predetermined angle at which the cassette is aligned with the pick and place robot (such as in Figs. 5 and 11). After wafer transport has been completed by the pick and place robot, further rotation of the worm gear from 180° to 360° will cause the port door and cassette to reverse their rotational direction and return to their imtial positions. In a prefeπed embodiment of the invention, the worm gear 138 and rotation link 140 may be sized and the pins 142 and 144 located in such a position that a 180° rotation of worm gear 138 from the approximate position shown in Fig. 9 will rotate the port door 104 approximately 35° from its initial position. However, it is understood that port door 104 may be made to rotate through an angle greater or less than 35° in alternative embodiments of the invention. One skilled in the art would appreciate how to vary the size of worm gear 138 and rotation link 140 and vary the position of pins 142 and/or 144 to vary the rotation of port door 104 with respect to elevator 106 to be less than or greater than 35°.

From the position shown in Fig. 9, counterclockwise rotation of the worm gear 138 will initially cause a clockwise rotation of the port door 104. Those skilled in the art would appreciate that the initial direction of rotation of the port door 104 may be reversed from that shown in Fig. 9 in several ways, including for example reversing the cuπent flow to the motor, or by moving worm gear 138 and rotation link 140 to the opposite side of the port door.

A further embodiment of the rotation drive mechanism, shown in Fig. 10, is similar to the embodiment of Fig. 9, except that drive gear 136 may be replaced by a riming belt 148 having a first end looped around a drive pulley 150 of rotation motor 134 and a second end looped around a driven pulley 152. Other components having like reference numerals to Fig. 9 are structurally and operationally identical to the embodiment described above with respect to Fig. 9. In another alternative embodiment, the motor 134, the drive gear 136 and worm gear 138 may be replaced by a pneumatic cylinder, a rack and a pinion, respectively. Reciprocation of the rack by the pneumatic cylinder causes rotation of the pinion. In this embodiment, the rotation link 140 may be attached to the pmion, such that rotation of the pmion by the rack causes the port door to rotate with respect to the elevator as described above with respect to Fig. 9.

Another embodiment of the rotation drive mechamsm is shown in Fig. 13. In this embodiment, components which are the same as those shown in Figs. 9 and 10 are designated with like reference numerals. This embodiment includes a rotation link 200 having a first pivotal mounting point 202 on the port door 104 and a second pivotal mounting point 204 on the elevator 106. The rotation drive mechanism 132 of Fig. 13 further includes a wheel 206 rotated by the timing belt 148. The wheel 206 includes a cam follower 208, which cam follower is received in a slot 210 in the rotation link 200. As would be appreciated by those skilled in the art, rotation of wheel 206 and cam follower 208 will cause the rotation link to pivot as a result of the cam follower being engaged within slot 210. Pivoting of the rotation link 200 will cause rotation of the port door with respect to the elevator.

Those skilled in the art will understand that other known rotation drive mechanisms may be substituted for those described above. Moreover, it is understood that components of the rotation drive mechamsms from one of the above-described embodiments may be substituted into the rotation drive mechanisms of others of the above-described embodiments. Additionally, although the rotation drive mechanism has been described above as being mounted on the port door, those skilled in the art will appreciate that the rotation drive mechamsm may alternatively be mounted in the elevator.

The present invention has thus far been described with respect to a semiconductor wafer cassette that is located within a SMIF pod on top of indexer 100. However, it is further contemplated that the present invention may be used to rotate a wafer cassette that is located directly on the port door 104 of the indexer 100 without any pod. In this embodiment, port door 104 lowers with the cassette resting directly thereon, and the port door rotates to align the cassette with a pick and place robot as described above. Moreover, it is contemplated that a sensor system be provided on a wafer cassette and the pick and place robot, which sensor system generates a signal to cease rotation of the port door when the cassette opening and robot are properly aligned. In this way, the wafer cassette may be provided in any rotational orientation with respect to port door 104, and the port door 104 would continue rotating until the sensor system indicates that the cassette and robot are aligned.

As shown in the top view of Fig. 11, the present invention provides greater flexibility within a processing or test station 158 in that the pick and place robot 122 need not be located directly in front of the indexer 100. The cassette support and rotation assembly 105 allows the wafer-carrying cassette

113 to be rotated such that an opening of the cassette lies substantially orthogonal to an axis of an arm 160 of the pick and place robot 122 even where the indexer 100 does not face the robot. As such, the indexer 100 may be positioned so as to allow other components such as a keyboard 162 to be included within the station 158. A further advantage of the present invention as shown in Fig. 12 is that a plurality of indexers may be provided within the station 158 with each of them including port doors configured to rotate a wafer- carrying cassette from its initial position on the indexer to a position where the opening of the cassette faces the pick and place robot. As such, the pick and place robot may access a plurality of wafer-carrying cassettes during a single test or fabrication process. While the present invention has thus far been described with respect to an indexer, it is understood that the present invention may be used with other devices that extract a wafer cassette from within a SMIF pod. For example, as shown in Fig. 14, the cassette support and rotation assembly may be used within a loadlock chamber 220. Details of such a loadlock chamber are disclosed in the '698 Application. As shown in Fig. 14, the loadlock chamber 220 includes a plurality of ports 222 located peripherally around the cylindrical chamber. Once the cassette 113 has been lowered into the chamber 220, the chamber may be sealed and evacuated. Thereafter, the ports 222 may be opened, and the cassette and/or wafers from within the cassette may be transferred through the ports via pick and place robots (not shown). In order to orient the cassette opening toward a particular port 222, the cassette may rest on a cassette support and rotation assembly 105 according to the present invention as described above.

In the embodiment shown in Fig. 14, the port door 104 is shown sealing the loadlock chamber. Thus, in this embodiment, tbe cassette is supported within the loadlock chamber on a support platform 224. The support platform includes the bearings and rotation drive mechamsm as described above with respect to Figs. 7-10 and 13, so that the support platform may rotate to controllably orient the cassette opening as desired. In an altemative emrxxiiment, the chamber may be sealed by the pod cover 114, and the cassette may rest on the port door, which is capable of rotating as described above. An altemative embodiment of the invention is shown in Fig. 15. In the embodiment of Fig. 15, components which are the same as those shown in Fig. 14 are designated with like reference numerals. In the embodiment shown in Fig. 15, the cassette may be supported on a support platform or port door as described with respect to Fig. 14. However, in this embodiment, the support platform (or port door) is fixedly mounted on the telescopic shaft 115. The shaft 115 is supported on bearings 226 mounted under the chamber. Additionally, the shaft includes teeth 228 around the diameter of the shaft, which teeth mesh with a drive gear 230. The drive gear 230 is in turn driven by a motor 232, which motor is controlled by the CPU 146. In this embodiment, the shaft may be controllably rotated to position the opening of the cassette 113 as desired with respect to the ports 222. Although not indicated in Fig. 15, the bearings 226, teeth 228, drive gear 230 and motor 232 may all be supported so as to move upwards and downwards with the shaft 115 as the shaft vertically translates.

The embodiment of the present invention shown in Fig. 15 may additionally operate within an indexer having a telescopic shaft as opposed to the lead screws 120 shown in Fig. 2. Where the indexer includes a cassette support and rotation assembly supported on a telescopic shaft, the port door may either be rotatably supported on the shaft (as in Fig. 14) or fixedly mounted on the shaft, with the shaft capable of controlled rotation (as in Fig. 15).

It is understood that the cassette support and rotation assembly according to the present invention may be included within other conventional cassette support platforms used in SMIF interface and/or SMIF transfer devices.

The invention has also thus far been described as rotating the port door about a central axis of the port door. However, it is further contemplated that the point about which the port door rotates be eccentrically located with respect to the rotational center of the port door. In this embodiment, once the port door has lowered the wafer cassette through the SMIF port, the port door can rotate about an eccentric axis so as to both rotate the wafer cassette and to swing the port door and wafer cassette partially out of the indexer. Support bearings of known configuration may be used to eccentrically and rotatably support the port door, and rotation of the port door may be accomplished with drive mechamsms similar to those described above with respect to the embodiment where the port door rotates about a central axis. An example of such an embodiment is shown in Fig. 16. Fig. 16 includes a rotation drive mechanism such as described above with respect to Fig. 8. A rotation motor 134 drives drive gear 136 affixed to an end of the motor 134. The drive gear 136, in turn, meshes with and drives worm gear 138 rotatably mounted on a bottom surface of port door 104. The rotation link 140 has a first end mounted by a pin 142 to an outer circumference of the worm gear and a second end mounted by a pin 144 to a bottom surface of the elevator 106. The cassette support and rotation assembly 105 of Fig. 16 further includes a door pivot 240 mounted to the elevator 106 and pivotally mounted to the port door 104. The assembly 105 in Fig. 16 further includes door support bearings 242, 244 that include wheels which support the port door 104 while allowing translation of the port door with respect to the support bearings 242, 244. Upon rotation of the drive gear 134, the rotation link 140 will cause the port door to rotate about the door pivot 240 so that the door swings to a position shown in phantom in Fig. 16. Although the invention has been described in detail herein, it should be understood that the invention is not limited to the embodiments herein disclosed. Various changes, substitutions and modifications may be made thereto by those skilled in the art without departing from the spirit or scope of the invention as described and defined by the appended claims.

Claims

I Claim:

1. A cassette support and rotation assembly in a semiconductor process station, the cassette support and rotation assembly supporting and rotating a cassette carrying a workpiece, comprising: a support platform for receiving the cassette through a port, and for supporting the cassette; elevation means capable of translating said support platform; bearing means between said support platform and said elevation for rotatably supporting said support platform on said elevation means; rotation drive means for rotating said support platform with respect to said elevation means; and control means for controlling operation of said rotation drive means.

2. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1 , wherein said support platform comprises a port door mitially located within and sealing a port on the semiconductor process station.

3. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said semiconductor process station comprises an indexer for determining and/or altering the vertical position of the workpiece in the cassette.

4. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said semiconductor process station comprises a loadlock chamber for transferring the cassette from atmospheric pressure to high-vacuum semiconductor fabrication processes.

5. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, further comprising at least one lead screw on which said elevation means is mounted, said at least one lead screw translating said elevation means.

6. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, further comprising a shaft on which said elevation means is mounted, said shaft capable of translation to translate said elevation means.

7. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said rotation drive means comprises: a power source; a power transfer mechanism, interconnected between said support platform and said elevation means, for being driven by said power source and for rotating said support platform with respect to said elevation means upon being driven by said power source.

8. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said rotation drive means comprises: a motor; a gear rotatably mounted to said support platform and rotated by said motor; a plurality of threads circumferencially provided around said elevation means, said gear meshing with said plurality of threads on said elevation means such that rotation of said gear causes rotation of said support platform with respect to said elevation means.

9. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said rotation drive means comprises: a power source; a gear rotatably mounted to said support platform and rotated by said power source; and a rotation link having a first end mounted to said gear and a second end mounted to said elevation means such that rotation of said gear causes rotation of said support platform with respect to said elevation means.

10. A cassette support and rotation assembly in a semiconductor process station as recited in claim 9, wherein said power source comprises a motor, said rotation drive mechanism further comprising a worm gear mounted on and rotating by said motor, said worm gear rotating said gear.

11. A cassette support and rotation assembly in a semiconductor process station as recited in claim 9, wherein said power source comprises a pneumatic cylinder, said rotation drive mechanism further comprising a rack mounted on and translated by said pneumatic cylinder, said rack rotating said gear.

12. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said rotation drive means comprises: a power source; a wheel rotatably mounted to said support platform and rotated by said power source; a cam follower eccentrically mounted on and extending from said wheel; and a rotation link having a first point pivotally mounted to said support platform, a second point pivotally mounted to said elevation means, and a slot, said cam follower engaged in said slot such that rotation of said cam follower on said wheel causes reciprocation of said rotation link and rotation of said support platform with respect to said elevation means.

13. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, further comprising: rotational position indicator mounted on said support platform; and a sensor for monitoring said rotational position indicator, said control means controlling said rotation drive means at least in part based on input from said sensor.

14. A cassette support and rotation assembly in a semiconductor process station as recited in claim 1, wherein said support platform rotates about a point different than a center axis of rotation of said support platform, such that said support platform rotates and translates with respect to said elevation means

15. A cassette support and rotation assembly for transferring a cassette carrying a workpiece through a SMIF port and rotating the cassette into alignment with a robotic transfer device, the cassette support and rotation assembly comprising: a movable port door located in the SMIF port prior to receiving the cassette, the port door including means for supporting the pod door and the cassette; means adjacent said port door for rotating the port door to locate an opening of the cassette at a predetermined orientation with respect to the robotic transfer device; an elevator for rotatably supporting said port door; and means for lowering said elevator, said port door, and the cassette through the SMIF port.

16. A cassette support and rotation assembly as recited in claim 15, wherein said means for rotating said port door comprises: a motor; a gear rotatably mounted to said port door and rotated by said motor; and a rotation link having a first end mounted to said gear and a second end mounted to said elevator such that rotation of said gear causes rotation of said port door with respect to said elevator.

17. A cassette support and rotation assembly as recited in claim 15, further including bearing means for rotatably supporting said port door on said elevator.

18. A cassette support and rotation assembly as recited in claim 17, wherein said elevator includes a central circular opening, and said bearing means comprise a plurality of bearings rotationally engaged around said central circular opening.

19. A cassette support and rotation assembly as recited in claim 17, said elevator further including a central opening having an angled extension around a circumference of said elevator defining said central opening, said bearing means comprising a plurality of wheels rotatably mounted to said port door, said plurality of rotating wheels having outer circumferences with V- shaped grooves for mating with said angled extension to thereby rotatably support said port door on said elevator.

20. A cassette support and rotation assembly as recited in claim 15, wherein said port door is capable of rotating before said elevator lowers said port door from an initial location of said port door in said SMIF port.

21. A cassette support and rotation assembly as recited in claim 15, wherein said port door is capable of rotating after said elevator lowers said port door from an initial location of said port door in said SMIF port.

22. A cassette support and rotation assembly as recited in claim 15, said lowering means comprising at least one lead screw, said elevator having a threaded opening for receiving said at least one lead screw.

23. A cassette support and rotation assembly as recited in claim 15, wherein said means for rotating said port door comprises: a motor; a power transfer mechanism, interconnected between said port door and said elevator, for being driven by said motor and for rotating said port door with respect to said elevator upon being driven by said motor.

24. A system for supporting and transferring a substrate used in semiconductor wafer fabrication, the substrate having an axis of rotation, the system capable of rotating the wafer about the axis of rotation, the system comprising: a plate including a port and a port door, said port door capable of sealing said port and said port door capable of supporting the wafer; a support means for rotatably supporting said port door; a lowering means connected to said support means for lowering said support means and said port door with respect to said plate; a rotating means interconnected between said support means and said port door for controllably rotating said port door with respect to said support means.

25. A system as recited in claim 24, wherein said support means comprises an elevator.

26. A system as recited in claim 24, wherein said lowering means comprises at least one lead screw, said at least one lead screw being received within at least one threaded opening, one lead screw per threaded opening, in said support means, wherein rotation of said at least one lead screw raises and lowers said support means.

27. A system as recited in claim 24, wherein said rotating means comprises: a motor; a power transfer mechanism, interconnected between said port door and said support means, for being driven by said motor and for rotating said port door with respect to said support means upon being driven by said motor.

28. A system as recited in claim 24, further comprising a processor for controUing operation of said motor.

29. A system as recited in claim 24, wherein said rotating means comprises: a motor; a gear rotatably mounted to said port door and rotated by said motor; and a rotation link having a first end mounted to said gear and a second end mounted to said support means, wherein rotation of said gear causes rotation of said port door with respect to said support means.

30. A system as recited in claim 24, wherein said rotating means comprises: a motor; a gear rotatably mounted to said port door and rotated by said motor; a plurality of threads located on an inner edge of said support means, said inner edge defining a center opening in said support means, said gear meshing with said plurality of threads on said inner edge of said support means such that rotation of said gear causes rotation of said port door with respect to said support means.

31. A system as recited in claim 24, wherein said rotating means is capable of rotating said port door with respect to said support means before said lowering means lowers said support means and port door with respect to said plate.

32. A system as recited in claim 24, wherein said rotating means is capable of rotating said port door with respect to said support means after said lowering means lowers said support means and port door away from said plate.

33. A system as recited in claim 24, wherein said rotating means is capable of rotating said port door with respect to said support means while said lowering means lowers said support means and port door with respect to said plate.

34. A system as recited in claim 24, wherein the substrate comprises a semiconductor wafer.

35. A system as recited in claim 24, wherein the substrate is supported within a cassette that is supported on said port door.

36. A system for supporting, transferring and rotating a substrate used in semiconductor wafer fabrication, the system including a power source, and the system comprising: a plate including a port and a port door, said port door capable of sealing said port and said port door capable of supporting the wafer; an elevator for rotatably supporting said port door, a lowering means engaging said elevator for lowering said elevator and said port door with respect to said plate; and a power transfer mechamsm, interconnected between said port door and said elevator, for being driven by the power source and for rotating said port door with respect to said elevator upon being driven by the power source.

37. A system for supporting, transferring and rotating a substrate as recited in claim 36, wherein said port door rotates about an axis of rotation substantially coaxial with an axis of rotation of said port door.

38. A system for supporting, transferring and rotating a substrate as recited in claim 36, wherein said port door rotates about an axis of rotation substantially eccentric with an axis of rotation of said port door.

39. A system for supporting, transferring and rotating a substrate as recited in claim 36, wherein said power transfer mechamsm is capable of rotating said port door with respect to said elevator before said lowering means lowers said elevator and port door with respect to said plate.

40. A system for supporting, transferring and rotating a substrate as recited in claim 36, wherein said power transfer mechamsm is capable of rotating said port door with respect to said elevator after said lowering means lowers said elevator and port door away from said plate.

41. A system for supporting, transferring and rotating a substrate as recited in claim 36, wherein said power transfer mechamsm is capable of rotating said port door with respect to said elevator while said lowering means lowers said elevator and port door with respect to said plate.