Abstract:
The present invention generally provides a robot that can transfer workpieces, such as silicon wafers, at increased speeds and accelerations and decelerations. More particularly, the present invention provides a robot wrist associated with the robot arm for mechanically clamping a workpiece to a workpiece handling member attached to the arm. The wafer clamp selectively applies sufficient force to hold the workpiece and prevent slippage and damage to the workpiece during rapid rotation and linear movement of the handling member. In a particular embodiment, a clamp for securing silicon wafers uses a flexure assembly to position and hold the wafer with minimal particle generation and wafer damage. The clamp is designed so that the wafers are normally clamped near full extension of the workpiece handling member to deliver or pick up a wafer. A particular embodiment uses a pneumatic cylinder to actuate the flexure assembly so that the flexure assembly moves outwardly and rearwardly away from the wafer when actuated at or near full extension of the workpiece handling member.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/272,658, which was filed on Mar. 18, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a clamping mechanism that secures a workpiece to a mechanical arm. More particularly, the present invention relates to a clamp that gently secures a semiconductor wafer to a robot blade by biasing the wafer against a retaining member at the forward edge of the blade when the robot blade is at least partially retracted for rotation. The clamp is actuated by a pneumatic cylinder and utilizes a flexure member to maintain a desirable clamping force against the wafer. 
     2. Background of the Related Art 
     Modern semiconductor processing systems include cluster tools which integrate a number of process chambers together in order to perform several sequential processing steps without removing the substrate from a highly controlled processing environment. These chambers may include, for example, degas chambers, substrate preconditioning chambers, cooldown chambers, transfer chambers, chemical vapor deposition chambers, physical vapor deposition chambers, etch chambers, and the like. The combination of chambers in a cluster tool, as well as the operating conditions and parameters under which these chambers are run, are selected to fabricate specific structures using a specific process recipe and process flow. 
     Once the cluster tool has been set up with a desired set of chambers and auxiliary equipment for performing certain process steps, the cluster tool will typically process a large number of substrates by continuously passing substrates through a series of chambers and process steps. The process recipes and sequences will typically be programmed into a microprocessor controller that will direct, control, and monitor the processing of each substrate through the cluster tool. Once an entire cassette of wafers has been successfully processed through the cluster tool, the cassette may be passed to yet another cluster tool or stand alone tool, such as a chemical mechanical polisher, for further processing. 
     Typical cluster tools process substrates by passing the substrates through a series of process chambers. In these systems, a robot is used to pass the wafers through a series of processing chambers. Each of the processing chambers is constructed to accommodate and process two wafers at a time. In this way, throughput of substrates in the cluster tool is effectively doubled. The amount of time required by each process and handling step has a direct impact on the throughput of substrates per unit of time. While the exact design of an integrated circuit fabrication system may be complex, it is almost always beneficial to perform each step as quickly as possible to maximize overall throughput without detrimentally affecting product quality, operating costs, or the life of the equipment. 
     Substrate throughput in a cluster tool can be improved by increasing the speed of the wafer handling robot positioned in the transfer chamber. As shown in FIG. 1, the magnetically coupled robot comprises a frog-leg type connection or arms between the magnetic clamps and the wafer blades to provide both radial and rotational movement of the robot blades in a fixed plane. Radial and rotational movements can be coordinated or combined in order to pick up, transfer, and deliver substrates from one location within the cluster tool to another, such as from one chamber to an adjacent chamber. 
     Another exemplary robot is shown in FIG.  2 . FIG. 2 shows a conventional polar robot with an embodiment of the substrate clamping apparatus of the present invention. As shown in FIG. 2, like the “frog-leg” type robot of FIG. 1, radial and rotational movements may be coordinated or combined in order to pick up, transfer, and deliver substrates from one location within a cluster tool to another, such as from one chamber to an adjacent chamber. However, unlike the robot in FIG. 1, the robot shown in FIG. 2 may also provide translational movement of wafer  302 . 
     As the robot speed and acceleration increase, the amount of time spent handling each substrate and delivering each substrate to its next destination is decreased. However, the desire for speed must be balanced against the possibility of damaging the substrate or the films formed thereon. If a robot moves a substrate too abruptly, or rotates the wafer blade too fast, then the wafer may slide off the blade, potentially damaging both the wafer and the chamber or robot. Further, sliding movements of the substrate on the wafer blade may create particle contaminants which, if received on a substrate, can contaminate one or more die and, thereby, reduce the die yield from a substrate. In addition, movement of the substrate on the wafer blade may cause substantial misalignment of the substrate that may result in inaccurate processing or even additional particle generation when the substrate is later aligned on the support member in the chamber. 
     The robot blade is typically made with a wafer bridge on the distal end of the wafer blade that extends upwardly to restrain the wafer from slipping over the end. However, the wafer bridge does not extend around the sides of the blade and does very little to prevent the wafer from slipping laterally on the blade. Furthermore, the wafers are not always perfectly positioned against the bridge. Sudden movement or high rotational speeds may throw the wafer against the bridge and cause damage to the wafer or cause the wafer to slip over the bridge and/or off the blade. 
     There is a certain amount of friction that exists between the bottom surface of a wafer and the top surface of the wafer blade that resists slippage of the wafer. However, the bottom surface of a silicon wafer is very smooth and has a low coefficient of friction with the wafer blade, which is typically made of nickel plated aluminum, stainless steel or ceramic. Furthermore, a typical wafer is so lightweight that the total resistance due to friction is easily exceeded by the centrifugal forces applied during rapid rotation of the robot, even when the blade is in the fully retracted position. However, this low coefficient of friction is typically relied upon when determining the speed at which a robot rotates. 
     Patent application Ser. No. 08/935,293, entitled “Substrate Clamping Apparatus,” filed on Sep. 22, 1997, which is hereby incorporated by reference discusses the problem of wafer slippage on a robot blade and the need to increase wafer transfer speeds. This application describes a clamping mechanism that holds the substrate on the blade during transfer. However, that invention is directed to a complex lever/flexure system to engage and disengage the clamp fingers. 
     Prior substrate clamping apparatus have also included pneumatically actuated clamp fingers in which a clamp finger assembly is actuated electronically through use of a solenoid when it is programmatically determined based on robot arm sensors that the robot arm is in the extended position. Such prior apparatus do not utilize flexure members in the gripping mechanism and may, accordingly, exert undue clamping forces against the wafer being secured to the blade. Such undue clamping forces may require moving parts such as bearings or slides to minimize particle generation upon engagement with the wafer. Such prior apparatus may utilize extension springs, compression springs, or other biasing members besides flexure members, which may generate more undesirable particles than use of flexure members. 
     There is a need for a robot that can transfer wafers at increased speeds and acceleration/decelerations, particularly in a multiple or single substrate processing system. More specifically, there is a need for a wafer clamping mechanism on a robot that can secure a wafer or a pair of wafers on a wafer blade or a pair of wafer blades with sufficient force to prevent wafer slippage and wafer damage during rapid rotation and radial movement while minimizing or eliminating undesirable particle generation. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention is directed to a clamp wrist for a robot assembly having one or more arms and one or more actuators for driving the arms to handle a workpiece, comprising: a wrist housing pivotally coupled to the arms; at least one clamp finger disposed in the wrist housing; and a biasing member coupled to the at least one clamp finger for urging the at least one clamp finger against the workpiece. A particular feature of this aspect of the invention is that the actuator may be a pneumatic cylinder. Further, the clamp finger may comprise a yoke, operatively connected to a piston rod of the pneumatic cylinder, and the yoke may be further operatively connected to at least one flexure member. Further, the flexure member may be connected to a tip end for engagement with an edge of the workpiece. 
     In another aspect, the invention may be directed to a clamping mechanism for securing a workpiece to a workpiece handling member coupled to the distal end of a robot arm, the workpiece handling member comprising a wafer handling blade having a workpiece receiving region and a retaining member at the distal end thereof, comprising at least one clamp finger adapted and positioned to contact the edge of the workpiece; and a biasing member coupled to the at least one clamp finger adapted to urge the at least one clamp finger against the workpiece when the workpiece is positioned on the workpiece receiving region to clamp the workpiece between the at least one clamp finger and the retaining member. A particular feature of this aspect of the invention is that the at least one clamp finger may further comprise a flexure assembly. The clamping mechanism may further comprise a pneumatic cylinder operatively connected to the flexure assembly to move the flexure assembly away from the wafer upon providing compressed air to the pneumatic cylinder. Still further, the flexure assembly may comprise: a yoke; a pair of tip ends; a flexure member connected between the pair of tip ends; and a tip flexure member connected between each of the tip ends and opposing apogee ends of the yoke. Another feature of the present invention is that the flexure member may also be connected proximate a medial point along the flexure member to the wrist housing, and the piston rod of the pneumatic cylinder may be rotatably mounted to the yoke so that the yoke is free to rotate about the axis of the piston rod. 
     In still another aspect, the invention may be directed to a robot arm assembly, comprising: a pair of frog-leg type robot arms, each arm having a distal end with a clamp wrist attached thereto; the clamp wrist comprising a wrist housing pivotally coupled to the robot arm; a flexure assembly disposed in the wrist housing adapted to positively grip a wafer; and a pneumatic cylinder disposed in the wrist housing and operatively connected to the flexure assembly to cause the flexure assembly to flex away from the wafer being gripped. A feature of this aspect of the invention is that the flexure assembly may be adapted to flex outwardly and rearwardly away from the wafer upon engagement of the flexure assembly by the pneumatic cylinder, and the flexure assembly may include at least one leaf spring. Another feature of this aspect of the invention is that the flexure assembly may be rotatably connected to a piston rod of the pneumatic cylinder. Still another feature of this aspect of the invention is that at least one of the flexure members may be affixed to the wrist housing to cause the tip ends to rotate outwardly as the flexure assembly is engaged by the pneumatic cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 is a top schematic view of a “polar” type robot arm for wafer handling showing the robot in retracted position and also showing the robot in extended position in phantom. 
     FIG. 2 is a top schematic view of a cluster tool having a “frog-leg” type robot for wafer handling showing the robot in retracted position and also showing the robot in extended position in phantom. 
     FIG. 3 is a bottom view of the clamp wrist assembly of a “frog-leg” type robot with the bottom cover plate partially removed, showing a first embodiment of the lever arrangement of the present invention in a release position near full extension. 
     FIG. 4 is a bottom view of the clamp wrist assembly of a “frog-leg” type robot with the bottom cover plate partially removed, showing a first embodiment of the lever arrangement of the present invention in a partially retracted, clamped, position. 
     FIG. 5 is a top view of the clamp wrist assembly of a “polar” type robot with no cover plate, showing a second embodiment of the lever arrangement of the present invention in a release position near full extension. 
     FIG. 6 is a top view of the clamp wrist assembly of a “polar” type robot with no cover plate, showing a second embodiment of the lever arrangement of the present invention in a partially retracted, clamped, position. 
     FIG. 7 is a bottom view of the clamp wrist assembly of a “frog-leg” type robot with the bottom cover plate partially removed, showing a third embodiment of the lever arrangement of the present invention in a release position near full extension. 
     FIG. 8 is a bottom view of the clamp wrist assembly of a “frog-leg” type robot with the bottom cover plate partially removed, showing a third embodiment of the lever arrangement of the present invention in a partially retracted, clamped, position. 
     FIG. 9 is a top view of the clamp wrist assembly of a “polar” type robot with no cover plate, showing a fourth embodiment of the lever arrangement of the present invention in a release position near full extension. 
     FIG. 10 is a top view of the clamp wrist assembly of a “polar” type robot with no cover plate, showing a fourth embodiment of the lever arrangement of the present invention in a partially retracted, clamped, position. 
     FIGS. 11 and 12 are top and cross sectional views of a wafer blade having a plurality of wafer support members. 
     FIG. 13A is a magnified partial cross sectional view of the wafer blade and a wafer support member as indicated in FIG.  9 . 
     FIG. 13B and 13C are magnified partial cross sectional views of alternate wafer support members that may be used instead of, or in combination with, the wafer support member of 
     FIG. 14 is a fragmentary view of a portion of an embodiment of clamp finger  90  showing a machined tip end in place of a roller. 
     FIG. 15 is a top schematic view of a “polar” type robot arm for wafer handling showing the robot in retracted position and also showing the robot in extended position in phantom, utilizing a single clamp finger. 
     FIG. 16 is a top view of the clamp wrist assembly of a “frog-leg” type robot with no cover plate, showing an embodiment utilizing a single clamp finger. 
     FIG. 17 is a top view of the clamp wrist assembly of a “frog-leg” type robot with no cover plate, showing an embodiment of the lever arrangement of the present invention in a release position near full extension, utilizing opposing sets of clamp fingers on opposing sides of the wafer. 
     FIG. 18 is a top view of the clamp wrist assembly of a “frog-leg” type robot with no cover plate, showing an embodiment of the lever arrangement of the present invention in a partially retracted, clamped, position, utilizing opposing sets of clamp fingers on opposing sides of the wafer. 
     FIG. 19 is a top view of the clamp wrist assembly of a “frog-leg” type robot with the top cover plate partially removed, showing an embodiment utilizing a pneumatically actuated flexure based gripping mechanism in a release position near full extension. 
     FIG. 20 is a top view of the clamp wrist assembly of a “frog-leg” type robot with the top cover plate partially removed, showing an embodiment utilizing a pneumatically actuated flexure based gripping mechanism in a partially retracted, clamped, position. 
     FIG. 21 is a top view of the clamp wrist assembly of a “polar” type robot with the top cover plate partially removed, showing an embodiment utilizing a pneumatically actuated flexure based gripping mechanism in a release position near full extension. 
     FIG. 22 is a top view of the clamp wrist assembly of a “polar” type robot with the top cover plate partially removed, showing an embodiment utilizing a pneumatically actuated flexure based gripping mechanism in a partially retracted, clamped, position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a schematic view of a “polar” type robot shown in a retracted position and shown in phantom in an extended position. The robot  10  includes a single robot arm  42  including a first strut  44  rigidly connected to a drive member  20 . A second strut  45  of the robot arm  42  is pivotally connected to the first strut  44  by an elbow pivot  46  and by a wrist pivot  50  to a workpiece handling member  60 . The structure of struts,  44  and  45 , and pivots,  46  and  50 , form a “polar” type robot arm  42  connecting the wafer handling member  60  to the drive member  20 . 
     Basic operation of “polar” type robots are conventional. First strut  44  moves rotationally in one of two modes. In a rotational mode, a linkage between the drive member  20  and second strut  45  and wafer handling member  60 , is disengaged so that upon rotation of first strut  44 , the entire robot arm  42  rotates without extension or retraction. In an extension mode, a linkage between the drive member  20  and second struts  45  and wafer handling member  60  is engaged so that, for example, as first strut  44  rotates clockwise, second strut  45  rotates counterclockwise and wafer handling member  60  rotates clockwise. This counter-rotation of the respective struts causes extension of the wafer handling member  60  with respect to the robot  10 . Reversal of the drive  20  causes first and second struts  44 ,  45  and wafer handling member  60  to rotate in the reverse directions to cause retraction of the wafer handling member  60 . 
     FIG. 2 shows a schematic diagram of an exemplary integrated cluster tool  400  useful for processing wafers  302  in tandem. Wafers  302  are introduced into and withdrawn from the cluster tool  400  through a loadlock chamber  402 . A robot  10  having a pair of wafer handling blades  64  is located within the cluster tool  400  to transfer the substrates between the loadlock chamber  402  and the various process chambers  404 . The robot arms  42  are illustrated in a retracted position so that the robot assembly can rotate freely within the transfer chamber  406 . The specific configuration of the cluster tool in FIG. 2 is merely illustrative and the system shown is capable of processing two wafers  302  at one time. However, the invention is equally applicable to single wafer transfer or robot assemblies such as the “polar” type robot described above and shown in FIG.  1 . In a preferred aspect of the invention, a microprocessor controller is provided to control the fabricating process sequence, conditions within the cluster tool, and operation of the robot  10 . 
     FIG. 2 also illustrates a “frog-leg” type, magnetically-coupled robot  10  shown in a retracted position and shown in phantom in an extended position. The robot  10  comprises two concentric rings magnetically coupled to computer-controlled drive motors for rotating the rings about a common axis. The robot  10  includes a pair of robot arms  42  each including a first strut  44  rigidly connected to a first magnetic drive  20 . A second strut  45  of the robot arm  42  is pivotally connected to the first strut  44  by an elbow pivot  46  and by a wrist pivot  50  to a workpiece handling member  60  and to a common rigid connecting member  190 . The structure of struts,  44  and  45 , and pivots,  46  and  50 , form a “frog-leg” type robot arm robot arm  42  connecting the wafer handling members  60  to the magnetic drives  20 . 
     When the magnetic drives  20  rotate in the same direction with the same angular velocity, the robot  10  also rotates about its rotational axis z, which is perpendicular to the plane of the diagram, in this same direction with the same angular velocity. When the magnetic drives  20  rotate in opposite directions with the same angular velocity, there is linear radial movement of the wafer handling members  60  to or from an extended position. The mode in which both motors rotate in the same direction at the same speed can be used to rotate the robot  10  from a position suitable for wafer exchange with one of the adjacent chambers to a position suitable for wafer exchange with another chamber. The mode in which both motors rotate with the same speed in opposite directions is then used to extend the wafer blade radially into one of the chambers and then extract it from that chamber. Some other combinations of motor rotation can be used to extend or retract the wafer blade as the robot is being rotated about axis x. A connecting member  190  attached at the pivot  50  to the second strut  45  and the workpiece handling members  60  extends between and connects the two workpiece handling members  60  and the robot arms  42 . The assembly of connecting member  190  and workpiece handling member  60  is collectively referred to as the wrist  80 . Movement of one arm assembly  42  relative to the support  190  is symmetrically duplicated by the other arm assembly  42  by means of a synchronization mechanism in connecting support  190 , such as a gear or belt mechanism. 
     FIGS. 3 and 4 show a partial bottom view of a first embodiment of a workpiece handling member  60  with the bottom cover plates partially removed and illustrate the internal working components of the clamp wrist  80  adapted for use on a “frog-leg” type robot. FIGS. 5 and 6 show a partial top view of a second embodiment of a workpiece handling member  60  without a cover and illustrate the internal working components of the clamp wrist  80  adapted for use on a “polar” type robot. FIGS. 3 and 5 show clamp fingers  90  in an extended, or release, position in which wafer handling members  60  are fully extended so that clamp fingers  90  are disengaged from wafer  302  for loading or unloading of wafer  302 . 
     Each of the workpiece handling members  60  has a wrist housing  199 , a wafer handling blade  64  and a clamp wrist  80 . The wrist housing  199  may include a top cover plate and a bottom cover plate that encase the internal moving components of the workpiece handling member  60 . The housing  199  is substantially rigid and is adapted to protect the workpiece handling member  60  components. The handling blade  64  extends from the forward end of the wrist housing  199  as an integral part thereof and is adapted to receive a wafer  302  thereon. A bridge, or retaining member,  70  (shown in FIGS. 1 and 2) extends upwardly from the end of the wafer blade  64  opposite the wrist housing  199  at the distal end of the wafer handling blade  64 , and is adapted to abut a wafer  302  disposed on the blade. An alternative embodiment discussed below with reference to FIGS. 17 and 18 includes a second set of clamp fingers at the distal end of the workpiece handling member  60 . 
     The clamp wrist  80  of the workpiece handling member  60  is comprised of a lever arrangement  109 , a biasing member  114 , and a pair of clamp fingers  90 . The biasing member  114  preferably is a spring connected between the pair of clamp fingers  90 . 
     The pair of clamp fingers  90  are preferably pivotally mounted to and disposed within wrist housing  199  in spaced relation to one another. The two clamp fingers  90  are preferably coupled together by means of biasing member  114 , to bias the clamp fingers  90  in a direction generally towards the workpiece, or wafer,  302 . The clamp fingers  90  are selected so that, when the clamping mechanism is in a clamped position, the clamp fingers  90  engage the edge of the wafer  302 . The distal ends of the clamp fingers  90  preferably include machined tip ends  94  or rollers  92  formed of a hard, wear-resistant material to minimize the friction between the clamp fingers  90  and the wafer  302 , thereby minimizing particle generation. Further, tip flexure members  93  may be provided proximate the distal ends of the clamp fingers  90  to absorb shock from the force of the clamp fingers  90  as they engage the wafer  302  to further minimize particle generation and/or to maintain additional clamping force between the clamp fingers  90  and the wafer  302 . As shown in FIGS. 15 and 16, it should be noted that a single clamp finger  90  may also be provided having multiple tip ends  94  or rollers  92  for engagement with wafer  302 . In the embodiments shown in FIGS. 15 and 16, retaining member  70  may be located at a suitable position proximate the distal end of wafer handling blade  64  opposite rollers  92  or tip ends  94  to secure wafer  302  on the blade, in which event the retaining member  70  may not be located at the distal end of the wafer handling blade  64 , but instead may be located anywhere along the periphery of the wafer  302  so long as it is generally opposite rollers  92  or tip ends  94 . As shown in the embodiment illustrated in FIG. 16, a single clamp finger  90  may also be slidably mounted to the clamp wrist  80 . 
     In the particular embodiment shown in FIGS. 3 and 4, the lever assembly, or lever arrangement  109  generally includes a first lever  120  which is an elongated lever having opposing ends. One end of the first lever  120  is fixedly or integrally connected to a first clamp finger  90 . Opposite the fixed or integral connection end  121  of the first lever  120 , the contact end  124  of the first lever  120  has a relatively flat portion associated therewith that defines a contact pad  122 . A translational member  125  may also be attached to first lever  120  for engagement with a contact pad  135  of second lever  130  described below. Although not shown, it should be noted that translational member  125  may be connected with second lever  130  instead of first lever  120  so that contact pad  135  of second lever  130  will be a second contact pad  135  connected with first lever  120 . The lever assembly, or lever arrangement  109 , may also include a second lever  130  which may be an elongated lever that is fixedly or integrally connected to a second clamp finger  90  at a connection end  131  and having a contact end  132  opposite its connecting end  131 . The first and second levers,  120  and  130 , are provided in angular relation and are adapted to pivot in the same plane along with the first and second clamp fingers  90 , respectively. The translational member  125  of the first lever  120  is adapted and positioned to abut and maintain contact between the contact pad  135  associated with the contact end  132  of the second lever  130  as the first lever  120  and the translational member  125  affixed thereto rotates in a forward direction. To minimize the friction and resulting particle generation between the contact pad  135  of the second lever  130  and the translational member  125  of the first lever  120 , the translational member  125  of the first lever  120  preferably includes a contact roller  126  rotatably attached thereto that is formed of a hard, wear-resistant material. In operation, pivotal movement of the first lever  120  and the translational member  125  connected thereto causes pivotal movement of the second lever  130 . A translational member  82  attached to the second strut  45  of the robot arm  42  is adapted to selectively mate with and engage the contact pad  122  of the first lever  120  to pivot the first clamp finger  90  away from the wafer  302  at a given degree of robot arm extension. 
     The translational member  82  is an elongated rigid member fixedly attached to the second strut  45  near the pivot  50  connecting the second strut  45  to the workpiece handling member  60 . The translational member  82  extends outwardly from the second strut  45  into the wrist housing  199 . Rotatably attached to an apogee end of the translational member  82  is a roller  84  adapted to abut another surface without generating substantial particles. The roller  84  is preferably formed of a hard, wear-resistant material to minimize the friction between the translational member  82  and the contact pad  122 . The translational member  82  is adapted and positioned so that its apogee end will abut the contact pad  122  of the first lever  120  as the apogee end of the translational member  82  rotates and moves generally forwards, towards the wafer  302  and the handling blade  64 . Extension of the robot arm  42  causes a forward rotation of the translational member  82 . 
     As translational member  82  mates and engages the contact pad  122  of the first lever  120  at a given degree of robot arm extension, the translational member  125  of the first lever  120  similarly mates and engages with contact pad  135  of second lever  130  to pivot the second clamp finger  90  away from the wafer  302  at a given degree of robot arm extension. Preferably, the translational member  125  of first lever  120 , the contour of contact pad  135  of second lever  130 , and the shapes of first and second clamp finger  90  are selected so that the angle of rotation of both the first and second clamp fingers  90  are the same at all times. 
     Referring now to the embodiment shown in FIGS. 5 and 6, the translational member  82  is fixedly attached to the second strut  45  near the pivot  50  connecting the second strut  45  to the workpiece handling member  60 . Rotatably attached to the translational member  82  is a roller  84  adapted to abut another surface without generating substantial particles. The roller  84  is preferably formed of a hard, wear-resistant material such as, for example PEEK (polyethyl ether ketone), or TUFSAM (teflon impregnated anodization coated aluminum), to minimize the friction between the translational member  82  and the contact pad  122 . The translational member  82  is adapted and positioned so that it will abut the contact pad  122  of the first lever  120  as the second strut  45  and the translational member  82  affixed thereto rotate with respect to wafer handling member  60  at or near full extension of wafer handling member  60 . Extension of the robot arm  42  causes a rotation of the first lever  120  to pivot the first clamp finger  90  away from the wafer  302  at a given degree of robot arm extension. 
     As translational member  82  mates and engages the contact pad  122  of the first lever  120  at a given degree of robot arm extension, the translational member  125  of the first lever  120  similarly mates and engages with contact pad  135  of second lever  130  to pivot the second clamp finger  90  away from the wafer  302  at a given degree of robot arm extension. Preferably, the translational member  125  of first lever  120 , the contour of contact pad  135  of second lever  130 , and the shapes of first and second clamp fingers  90  are selected so that the angle of rotation of both the first and second clamp fingers  90  are the same at all times. 
     FIGS. 3 and 4 are bottom views of the clamp wrist  80  with the bottom cover plate  202  removed and show the clamp wrist  80  operation with the robot arms  42  of a “frog-leg” type robot in an extended and retracted position, respectively. Similarly, FIGS. 5 and 6 are top views of the clamp wrist  80  with no cover plate, and show the clamp wrist  80  operation with the robot arms  42  of a “polar” type robot in an extended and retracted position, respectively. The comparison of the figures is useful to show how the clamp mechanism releases the wafer at full extension. FIGS. 4 and 6 show the wrist assembly  60  in a fully retracted position over the hub of the robot, such as when the assembly is in position for rotation. The clamp fingers  90  are engaged against the perimeter of the wafer  302  in the clamped position. The engagement of the clamp fingers  90  not only clamps the wafer  302 , but also consistently and accurately positions the wafer on the blade  64 . Because the wafer  302  is accurately positioned, there are fewer handling errors and no need to use sophisticated wafer center finding equipment, although such equipment could still be used. When the wrist  80  is fully retracted, the proximal distance between the translational member  82  and the mating contact pad  122  of first lever  120  is at a maximum. 
     FIGS. 3 and 5 show the blade  64  and wrist  80  extended through a wafer transfer slot  410  in a wall  412  of a chamber  404  (FIG. 2) to a point where the clamping mechanism is released. Note the gaps between the rollers  92  of clamp fingers  90  and the edge of the wafer  302  that allow the wafer to be lifted from the top of the blade  64  by another apparatus, such as lift pins of a processing chamber (not shown). It is also instructive to note the relative positions of the translational members  82 ,  125 , the levers  120 ,  130 , stop members  150 ,  151  (described below), and the spring, or other biasing member,  114 . In this release position, the spring, or other biasing member,  114  is extended. The spring, or other biasing member,  114  normally biases the contact fingers  90  in a direction generally toward wafer  302  to engage with and secure wafer  302  against retaining member  70  when the wrist assembly  60  is in a fully retracted position over the hub of the robot, such as when the assembly is in position for rotation (FIGS.  4  and  6 ). However, the force of translational member  82  as it engages with the lever arrangement  109  acts against the biasing force of the spring, or other biasing member,  114  to disengage clamp fingers  90  from the wafer  302  at a given degree of robot arm extension. 
     Outer stop member  150  comprises a fixed stop attached to the top cover plate  200 , and limits the outward movement of the first and second clamping fingers  90 . The stop member  150  is adapted and positioned to prevent outward motion of the clamping fingers  90  beyond a predetermined position. This position is determined by the required travel away from the wafer  302  of the clamp fingers  90  to desirably release wafer  302 . In some instances, the robot  10  must retrieve a misaligned wafer  302  and the clamping mechanism serves to align a wafer  302  as it grips the wafer on the handling blade  64 . Thus, the clamp fingers  90  must sufficiently retract to allow a misaligned wafer  302  to be placed on the wafer blade  64 . In the preferred embodiment, the outer stop member  150  is positioned to permit the clamp fingers  90  to retract up to 0.160 inches which will accommodate a wafer misalignment of up to 0.080 inches from center. The amount of retraction can be adjusted to accommodate tolerances in specific systems and is specifically limited in one embodiment to obtain substantial life from the spring, or other biasing member,  114 , and to prevent damage to tip flexure members  93 . However, the amount of retraction can be any amount dictated by the particular system in which the clamping assembly is utilized. Similarly, inner stop member  151  may be provided to limit the inward movement of the first and second clamping fingers  90 . The inner stop member  151  is adapted and positioned to prevent inward motion of the clamping fingers  90  beyond a predetermined position to, for example, prevent misalignment of lever arrangement  109 . 
     FIGS. 7 and 8 show a partial bottom view of a third embodiment of workpiece handling member  60  with the bottom plate partially removed and exposing the internal working components of the clamp wrist  80 , and is adapted for use on a “frog-leg” type robot. FIGS. 9 and 10 show a fourth embodiment of a workpiece handling member  60  without a cover, exposing the working components of clamp wrist  80  adapted for use on a “polar” type robot. FIGS. 7 and 9 show clamp fingers  90  in an extended, or release, position in which wafer handling members  60  are fully extended so that clamp fingers  90  are disengaged from wafer  302  for loading or unloading of wafer  302 . 
     In the embodiments shown in FIGS. 7-10, the lever assembly, or lever arrangement,  109  generally includes a translational lever  200 , which is an elongated lever having opposing ends. A pivoting end of the translational lever  200  is pivotally mounted to and disposed within wrist housing  199  and adapted to pivot in the same plane as clamp fingers  90 . Translational lever  200  further comprises a relatively flat portion associated therewith that defines a contact pad  220 . A translational member  208  may also be attached to the translational lever  200  for engagement with a contact pad  240  of flexure arrangement  245  described below. Translational member  208  preferably includes a contact roller  210  rotatably attached thereto that is formed of a hard, wear-resistant material such as, for example, PEEK (polyethyl ether ketone), or TUFSAM (teflon impregnated anodization coated aluminum). 
     Flexure arrangement  245  comprises a central contact portion  242 , having opposing ends to which flexure segments  230  are fixedly connected and from which flexure segments  230  extend to and fixedly connect to proximal ends of clamp fingers  90 . 
     The translational member  208  of translational lever  200  is adapted and positioned to abut and maintain contact between the contact pad  240  associated with contact portion  242  of the flexure arrangement  245  as the translational lever  200  and the translational member  208  affixed thereto rotate in a forward direction. In operation, pivotal movement of the translational lever  200  and the translational member  208  connected thereto causes forward movement of the contact portion  242  of the flexure arrangement  245  and associated flexure of flexure segments  230  attached thereto. Forward movement of flexure segments  230  causes inward movement of the ends of clamp fingers  90  to which the flexure segments  230  are attached and cause the clamp fingers  90  to pivot so that the distal ends of clamp fingers  90  move outward away from wafer  302 . A translational member  82  attached to the second strut  45  of the robot arm  42  is adapted to selectively mate with and engage the contact pad  122  of the first lever  120  to pivot the first clamp finger  90  away from the wafer  302  at a given degree of robot arm extension. 
     Referring now to the embodiment shown in FIGS. 7 and 8, the translational member  82  is an elongated rigid member fixedly attached to the second strut  45  near the pivot  50  connecting the second strut  45  to the workpiece handling member  60 . The translational member  82  extends outwardly from the second strut  45  into the wrist housing  199 . Pivotally attached to an apogee end of the translational member  82  is a roller  84  adapted to abut another surface without generating substantial particles. The roller  84  is preferably formed of a hard, wear-resistant material such as, for example, PEEK or TUFLAM coated aluminum, to minimize the friction between the translational member  82  and the contact pad  122 . The translational member  82  is adapted and positioned so that its apogee end will abut the contact pad  220  of the translational lever  200  as the apogee end of the translational member  82  rotates and moves generally forward, towards the wafer  302  and the handling blade  64 . Extension of the robot arm  42  causes a forward rotation of the translational member  82 . 
     As translational member  82  mates and engages the contact pad  220  of the translational lever  200  at a given degree of robot arm extension, the translational member  208  of the translational lever  200  similarly mates and engages with contact pad  240  of contact portion  242  to move flexure arrangement  245  forward towards wafer  302  and to thereby pivot clamp fingers  90  away from the wafer  302  at a given degree of robot arm extension. Preferably, the translational member  208  of translational lever  200 , the contour of contact pad  220  of translational lever  200 , the contour of contact pad  240  of flexure arrangement  245 , and the shapes of the clamp fingers  90  are selected so that the angle of rotation of the clamp fingers  90  are the same at all times. 
     Referring now to the embodiment shown in FIGS. 9 and 10, the translational member  82  is fixedly attached to the second strut  45  near the pivot  50  connecting the second strut  45  to the workpiece handling member  60 . Rotatably attached to the translational member  82  is a roller  84  adapted to abut another surface without generating substantial particles. The roller  84  is preferably formed of a hard, wear-resistant material such as, for example, PEEK or TUFLAM coated aluminum, to minimize the friction between the translational member  82  and the contact pad  122 . The translational member  82  is adapted and positioned so that it will abut the contact pad  122  of the first lever  120  as the second strut  45  and the translational member  82  affixed thereto rotate with respect to wafer handling member  60  at or near full extension of wafer handling member  60 . Extension of the robot arm  42  causes a rotation of the translational member  82 . 
     As translational member  82  mates and engages the contact pad  122  of the first lever  120  at a given degree of robot arm extension, the translational member  125  of the first lever  120  similarly mates and engages with contact pad  135  of second lever  130  to pivot the second clamp finger  90  away from the wafer  302  at a given degree of robot arm extension. Preferably, the translational member  125  of first lever  120 , the contour of contact pad  135  of second lever  130 , and the shapes of first and second clamp finger  90  are selected so that the angle of rotation of both the first and second clamp fingers  90  are the same at all times. 
     FIGS. 7 and 8 are bottom views of the clamp wrist  80  with the bottom cover plate  202  removed and show the clamp wrist  80  operation with the robot arms  42  of a “frog-leg” type robot in an extended and retracted position, respectively. Similarly, FIGS. 9 and 10 are top views of the clamp wrist  80  with no cover plate, and show the clamp wrist  80  operation with the robot arms  42  of a “polar” type robot in an extended and retracted position, respectively. The comparison of the figures is useful to show how the clamp mechanism releases the wafer at full extension. FIGS. 8 and 10 show the wrist assembly  60  in a fully retracted position over the hub of the robot, such as when the assembly is in position for rotation. Note that the clamp fingers  90  are engaged against the perimeter of the wafer  302  in the clamped position. The engagement of the clamp fingers  90  not only clamps the wafer  302 , but also consistently and accurately positions the wafer on the blade  64 . Because the wafer  302  is accurately positioned, there are fewer handling errors and no need to use sophisticated wafer center finding equipment, although such equipment could still be used. Also note that when the wrist  80  is fully retracted, the proximal distance between the translational member  82  and the mating contact pad  220  of translational lever  200  is at a maximum. Similarly, the proximal distance between the translational member  208  of translational lever  200  and the mating contact pad  240  of flexure arrangement  245  is at a maximum. 
     FIGS. 7 and 9 show the blade  64  and wrist  80  extended through a wafer transfer slot  410  in a wall  412  of a chamber  404  (FIG. 2) to a point where the clamping mechanism is released. Note the gaps between the rollers  92  of clamp fingers  90  and the edge of the wafer  302  that allow the wafer to be lifted from the top of the blade  64  by another apparatus, such as lift pins of a processing chamber (not shown). It is also instructive to note the relative positions of the translational members  82  and  208 , translational lever  200 , flexure arrangement  245 , flexure segments  230 , stop members  150 ,  151 , and the spring, or other biasing member,  114 . In this release position, the spring, or other biasing member,  114  is extended. The spring, or other biasing member,  114  normally biases the contact fingers  90  in a direction generally toward wafer  302  to engage with and secure wafer  302  against retaining member  70  when the wrist assembly  60  is in a fully retracted position over the hub of the robot, such as when the assembly is in position for rotation (FIGS.  8  and  10 ). However, the force of translational member  82  as it engages with the translational lever  200  and the resultant force of translational lever  200  as it engages with the flexure arrangement  245  acts against the biasing force of spring, or other biasing member,  114  to disengage clamp fingers  90  from the wafer  302  at a given. degree of robot arm extension. 
     Outer stop member  150  comprises a fixed stop attached to the top cover plate  200 , and limits the outward movement of the first and second clamping fingers  90 . The stop member  150  is adapted and positioned to prevent outward motion of the clamping fingers  90  beyond a predetermined position. This position is determined by the required travel away from the wafer  302  of the clamp fingers  90  to desirably release wafer  302 . In some instances, the robot  10  must retrieve a misaligned wafer  302 . The clamping mechanism serves to align these wafers  302  as it grips them on the handling blade  64 . Thus, the clamp fingers  90  must sufficiently retract to allow a misaligned wafer  302  to be placed on the wafer blade  64 . In the preferred embodiment, the outer stop member  150  is positioned to permit the clamp fingers  90  to retract up to 0.160 inches which will accommodate a wafer misalignment of up to 0.080 inches from center. The amount of retraction can be adjusted to accommodate tolerances in specific systems and is specifically limited in one embodiment to obtain substantial life from spring, or other biasing member,  114 , and to prevent damage to tip flexure members  93 . However, the amount of retraction can be any amount dictated by the particular system in which the clamping assembly is utilized. Similarly, inner stop member  151  may be provided to limit the inward movement of the first and second clamping fingers  90 . The inner stop member  151  is adapted and positioned to prevent inward motion of the clamping fingers  90  beyond a predetermined position to, for example, prevent misalignment of lever arrangement  109 . 
     FIGS. 11 and 12 are top and side cross sectional views of a wafer blade  64  having a plurality of wafer support members  74 . The wafer support members  74  are coupled to, or integrally formed in, the wafer blade  64  and have a wafer contact surface  76  that extends upward a sufficient distance above the top surface of the wafer blade  64  to prevent the bottom surface of the wafer  302  from contacting the top surface of wafer blade  64 . In this manner, the wafer support members  74  reduce the degree to which the bottom surface of the wafer  302  is contacted and rubbed, thereby decreasing the likelihood or degree of particle generation and/or wafer damage. 
     Although a wafer could be supported on as few as three wafer support members  74 , it is preferred that the wafer blade  64  include at least four wafer support members  74 . It is also generally preferred that the wafer support members  74  be spread out by as great a distance as is practical in order to provide stability to the wafer  302  received thereon, even though additional stability will be provided when the wafer is clamped. A plurality of support members  74  which preferably have a convex surface with a large radius reduce the contact pressure with the underside surface of the wafer  302  thereby further reducing the possibility of particle generation. Further, it should be noted that the blades of the robot may also be sloped so that the wafer has only edge contact with the blade. This may serve to reduce the friction between the wafers and the blades, thereby reducing the force required to push the wafers into position. 
     While the support members  74  may be made from any material, it is generally desirable to select a material that does not corrode in the process environment, erode or generate particles therefrom, and does not damage the wafer surface. Materials preferred for use as support members include alumina, blue sapphire, zirconia, silicon nitride and silicon carbide. The support members  74  may also be made from a machined metal having a ceramic, sapphire or diamond coating disposed thereon. 
     FIG. 13A is a magnified partial cross sectional view of the wafer blade  64  and a wafer support member  74  as indicated in FIG.  9 . The support member  74  in FIG. 13A is shown as a ball bearing that can rotate within bearing surface  78 . Because the bearings are free to rotate or roll, the degree of friction between the member  74  and the wafer  302  may be further reduced or eliminated. 
     FIGS. 13B and 13C are partial cross sectional views of alternative support members  74  that may be used instead of or in combination with the support member  74  shown in FIG.  13 A. The support member  74  of FIG. 13B comprises a post that is rigidly received within a hole in the blade  64  and a semi-spherical button which forms the top surface  76  that contacts the wafer  302 . The support member  74  of FIG. 13C is a ball or sphere that is rigidly secured within a hole in the blade so that the top surface  76  extends slightly above the top surface  66  of the blade  64 . Each of the designs in FIGS. 13A,  13 B, and  13 C or their equivalents may be used alone or in combination to provide support for the wafer  302 . Similarly, as shown in FIGS. 19-20, the robot blade may also include two pins  800 , pressed into the front end of the blade. The pins  800  rotatably support two rollers  810  preferably made of Vespel. The rollers  810  minimize the friction between the wafer  302  and pins  800 , allowing for better lateral capture of the wafer  302 . The blade may also have pads  820 , preferably made of Vespel, upon which the wafer  302  rests. The Vespel pads  820  ensure non-metallic contact with the wafer  302 , and minimize particle generation. Preferably, the Vespel pads  820  have a tapered “teardrop” shape, as shown, for assisting in the capture and retention of the wafer  302  on the wafer blade  64 , and further include an aperture therethrough for mounting the pads  820  to the wafer blade  64 . 
     FIGS. 19 and 20 show an embodiment of a workpiece handling member  60  having pneumatically actuated clamp fingers  90  and illustrate the internal working components of the clamp wrist  80  adapted for use on a “frog-leg” type robot. A dual wafer embodiment is shown. However, the invention can also be implemented on a single wafer “frog leg” type robot which is typically used in a Centura® System available from Applied Materials, Inc. located in Santa Clara, Calif. FIGS. 21 and 22 show an embodiment of a workpiece handling member  60  without a cover and illustrate the internal working components of the clamp wrist  80  adapted for use on a “polar” type robot. FIGS. 19 and 21 show clamp fingers  90  in an extended, or release, position in which wafer handling members  60  are fully extended so that clamp fingers  90  are disengaged from wafer  302  for loading or unloading of wafer  302 . 
     Each of the workpiece handling members  60  has a wrist housing  199 , a wafer handling blade  64  and a clamp wrist  80 . The wrist housing  199  may include a top cover plate and a bottom cover plate that encase the internal moving components of the workpiece handling member  60 . The housing  199  is substantially rigid and is adapted to protect the workpiece handling member  60  components. The handling blade  64  extends from the forward end of the wrist housing  199  as an integral part thereof and is adapted to receive a wafer  302  thereon. A pin, or retaining member,  800  (shown in FIGS. 19-22) extends upwardly from the end of the wafer blade  64  opposite the wrist housing  199  at the distal end of the wafer handling blade  64 , and may include a roller of, for example, Vespel or other suitable material. The roller is adapted to abut a wafer  302  disposed on the blade. Alternatively, the roller  810  and pin  800  may be an integral protrusion extending from the wafer blade  64  and may be made of ceramic or other suitable materials for assistance in capturing and retaining the wafer  302  on the wafer blade  64 . 
     The clamp wrist  80  of the workpiece handling member  60  is comprised of a flexure assembly  500  and a pneumatic cylinder  600 . The flexure assembly includes two clamp fingers  90 , integrated to form a single yoke  510 ; a mounting plate  530 , which is mounted to the wrist housing  199 ; a biasing member  114 , which is preferably a leaf spring flexure member  114  connected to the mounting plate  530  and a pair of tip ends, or jaws,  94 ; and a pair of tip flexure members  93 , which are preferably leaf spring flexure members  93  connected between an apogee end of the yoke  510  and the tip end, or jaw,  94 . The mounting plate  530  is preferably affixed to the wrist housing  199  and extends away from the wrist housing  199  so that the biasing flexure member  114  is affixed thereto preferably at a point medial to the flexure member  114 . Alternatively, dual flexure members  114  may be provided affixed to and extending from the flexure mounting plate  530 . The tip ends, or jaws,  94  are affixed to the distal ends of the flexure member, or members,  114  and are preferably tapered or curved to beneficially mate with and engage the wafer edge upon engagement of the flexure assembly  500  against the wafer  302  as described hereinafter. 
     The flexure assembly  500  is preferably mounted at a position on the wrist housing  199  and the tip ends  94  are suitably sized and selected such that the flexure assembly  500  must be retracted, or disengaged, to permit placement or removal of the wafer on the wafer handling blade  64 . In other words, the flexure assembly  500  provides a positive engagement of a wafer on the wafer handling blade  64 , and the flexure assembly  500  must be actively disengaged to release the wafer. Accordingly, unless actuated, the flexure assembly  500  is always exerting a clamping force against the wafer  302 . The clamping force with which the jaws  94  hold the wafer can be controlled by controlling the flexure stiffness and the length of the jaws  94  and flexures. 
     Tip flexure members  93  extend rearward from the tip ends, or jaws,  94  and are affixed to apogee ends of the yoke  510 . The yoke  510  is not affixed directly to the wrist housing. Instead, the yoke is rotatably mounted to the piston rod  610  of the pneumatic cylinder  600 , which preferably extends from the pneumatic cylinder  600  in a direction towards the flexure assembly  500  and wafer  302 . The yoke includes a bushing  620 , which is preferably manufactured of Delrin-AF or other suitable materials to permit free rotation of the yoke  510  about the piston rod  610  of the pneumatic cylinder  600  with minimal particle generation. This prevents undesirable twisting of the flexures  93 ,  114  about the axis of the pneumatic cylinder  600  in the event that the components are not perfectly sized and/or aligned. The cylinder  600  is mounted or otherwise affixed to the housing  199  and may preferably be mounted to the housing  199  by use of a mounting bracket  700 , which, as shown, is preferably integral with the mounting plate  530 . 
     The tip ends, or jaws,  94  are either machined from or include rollers  810  formed of a hard, wear-resistant material, such as Vespel or other suitable materials, to minimize the friction between the clamp fingers  90  and the wafer  302 , thereby minimizing particle generation. The tip flexure members  93  and flexure  114  may also absorb shock from the force of the clamp fingers  90  as they engage the wafer  302  to further minimize particle generation and/or to maintain additional clamping force between the clamp fingers  90  and the wafer  302 . 
     Method of Operation 
     In operation, the robot  10  rotates about its axis within the transfer chamber  406  to align the wafer handling members  60  with the various chambers  404  attached to the transfer chamber  406 . Once aligned with a chamber  402  and  404 , the robot arms  42  extend, by relative rotation of the first and second struts,  44  and  45 , moving the wafer handling members  60  and the wafers  302  resting thereon into the chamber  404  for transfer. To facilitate faster transfer of the wafers  302  between the chambers  404 , the wafers  302  are clamped on the wafer handling members  60  when resting thereon. The clamp wrist  80  used to facilitate this clamping operates as follows. While the following description refers to only a single robot arm  42 , clamp wrist  80 , and workpiece handling blade  64  for ease of description, it should be understood that operation of dual blades occurs in the same manner at each blade. 
     During wafer transfer on the wafer handling member  60 , the spring, or other biasing member  114  biases the clamp fingers  90  into the clamping position. Only when a sufficient force is applied to the spring, or other biasing member,  114 , will the attached clamp fingers  90 , move outward and away from the wafer  302 . In the preferred embodiment, the spring, or other biasing member,  114  exerts a clamping force on the wafer  302  of approximately 0.14 pounds, or about 1.2 times the weight of the wafer  302  Because the size of the wafers  302  are substantially constant, the clamping position of the clamp fingers  90  does not need to change. Thus, the clamp wrist  80  limits the inward and outward travel of the clamp finger  90 . Using the apparatus described, which connects the two contact fingers  90  associated with each wafer  302 , both of the clamp fingers  90  can be retracted using the motion of a single robot arm  42 . 
     Accordingly, the spring, or other biasing member,  114 , biases the clamp fingers  90  to an inward, clamped position in contact with a wafer  302  on the wafer handling blade  64 . However, in order to place the wafer  302  on and remove the wafer  302  from the wafer handling blade  64 , the clamping action must be released and the clamping fingers  90  retracted. The majority of the time that the wafer  302  is on the blade  64 , the robot  10  is moving the wafer  302 . To maximize the efficiency of the robot transfer, the wafer  302  is clamped as long as possible while it is on the handling blade  64  so that the robot  10  can use higher velocities and greater accelerations and decelerations to move the wafer  302  faster. Therefore, the clamping force is released only to accomplish wafer transfer between the wafer handling blade  64  and the chamber  404 . As such, the clamping force is released only when the robot arms  42  are extended into the chamber  404  to complete the transfer. 
     As the robot arms  42  extend into the chamber  404  to complete the transfer between the robot  10  and the chamber  404 , the struts,  44  and  45 , rotate relative to the workpiece handling member  60 . This rotation of the second strut  45  causes a relative rotation of the translational member  82  fixedly attached thereto. The translational member  82  is positioned and adapted so that, when the second strut  45  reaches a predetermined degree of rotation which translates to a given extension of the robot arms  42 , the roller  84  attached to the apogee end of the translational member  82  contacts the contact pad  122  of the first lever  120  causing a pivot of the first lever  120  on continued extension of the robot arm  42 . Accordingly, the translational member  82  translates the extending motion of the robot arm  42 , and the rotational motion of the struts,  44  and  45 , into a forward rotation of the first lever  120 . The translational member  125  of the first lever  120  then engages the contact pad  135  of second lever  130 , which also biases the second lever  130  forward causing forward rotation of the second lever  130 . As the first lever  120  and second lever  130  rotate forward, they cause the attached contact fingers  90  to move away from the wafer  302  and the handling blade  64 . The wafer  302  may then be removed from the wafer handling blade  64 . The subsequent retraction of the robot arms  42  causes the translational member  82  to disengage the first lever  120 , and allow the spring, or other biasing member,  114  to return the clamp fingers  90  to the clamped position and causing the clamp fingers  90  to engage the edge of the wafer  302  resting on the wafer handling blade  64 , thereby pressing the wafer  302  against the retaining member  70 . The spring, or other biasing member,  114  thus biases the workpiece handling members  60  to the clamped position. By biasing the wafer  302  against a retaining member  70  fixed to the handling blade  64 , the clamping fingers  90  align the wafer  302  to the same position each time a wafer  302  is placed on the handling member  64  and, thereby, increase the repeatability of the system. 
     Before reaching the position where the clamp fingers  90  retract, the robot movement is slowed to avoid any movement of the wafer  302  on the wafer handling blade  64 . When clamped, however, the robot movement speeds, accelerations, and decelerations are limited only by the robot movement capabilities. 
     One important design consideration of the present invention is that, in some cluster tools  400 , as in the one shown in FIG. 2, the processing chambers  404  and the loadlock chamber  402  may or may not be the same distance from the axis x of the robot  10 . The present invention accommodates this difference by the use of stop member  150 . As the spring, or other biasing member,  114  biases the contact fingers  90  outward, upon reaching a given outward position, the contact fingers  90  contact the stop members  150 , which prevents further outward travel of the contact fingers  90 . In particular embodiments, lever arrangement  109  may include at least one flexure portion, which may include flexure segments  230  of the embodiment shown in FIGS. 6-7, and  13 - 14 , to absorb any “lost motion” from further travel of robot arm  45 . 
     The exact point at which the clamping mechanism releases the wafer  302  is dependent upon, and may be determined by, the relative sizes and positioning of the various components. For example, the angle at which the translational member  82  is attached to the second strut  45  and the relative position of the contact pad  122  determine the relative position at which they contact one another. The relative lengths of the struts,  44  and  45 , determine the relative rotation of the second strut  45  to the workpiece handling member  60 . Because the clamp fingers  90  release at a given relative angle between the second strut  45  and the workpiece handling member  60 , the lengths of the struts,  44  and  45 , must be such that the angle is reached only when the robot arms  42  are extended. Other factors that may affect the point at which the clamping fingers  90  retract include the tension of the spring  114  and the relative positions of the first lever  120 , the second lever  130 , and the contact pad  135  of second lever  130 . In the preferred embodiment, these components are adapted so that the clamp fingers  90  retract when the wafer handling blade  64  is within 1 to 3 inches of the transfer position (i.e., the fully extended position). 
     When the clamp fingers  90  engage the wafer  302 , the wafer  302 , is secured between the fingers  90  and the retaining member  70 , then the engagement of the clamp fingers  90  will push the wafer  302  until it moves against the retaining member  70 . It is during this movement of the wafer  302  relative to the wafer blade  64  that the bottom surface of the wafer  302  will encounter any frictional forces with the wafer contact surface  76  of the wafer support members  74 . However, unlike support members of conventional blades which contact the wafer  302  over a large area, the support members of the present invention reduce or minimize the degree of contact and friction therebetween and, thereby, reduce or eliminate wafer damage or particle generation. Consequently, the wafer support members  74  of the present invention are not relied on to provide friction, but rather to reduce friction and damage to the wafer  302 . It is the clamping action of the present invention that holds the wafer  302  in place during movement of the blade  64 . 
     Referring now to FIGS. 17 and 18, it should be noted that any of the embodiments of the present invention may also include opposing clamp fingers  90 ,  690  or sets of clamp fingers  90 ,  690 , which could include a first, proximal, set of clamp fingers  90 , and a second, distal, set of clamp fingers  690  located on opposing sides of the wafer  302 . FIGS. 17 and 18 show a partial top view of an embodiment of a workpiece handling member  60  with no cover plate illustrating the internal working components of the clamp wrist  80 . The embodiment shown in FIGS. 17 and 18 is adapted for use on a “frog-leg” type robot, but it should be noted that opposing sets of clamp fingers  90 ,  690  could be used in any of the other embodiments described herein. FIG. 17 shows clamp fingers  90 ,  690  in an extended, or release, position in which wafer handling members  60  are fully extended so that clamp fingers  90 ,  690  are disengaged from wafer  302  for loading or unloading of wafer  302 . 
     In the embodiment shown in FIGS. 17 and 18, retaining member  70  (shown in FIGS. 1 and 2) is not used. Instead, the wafer  302  is abutted on either side by opposing clamp fingers  90 ,  690 . Preferably, the opposing sets of clamp fingers  90 ,  690  are operatively connected by common linkage  98 , which may be a length of wire, a segment of spring steel, or other suitable member. 
     In operation of the embodiment shown in FIGS. 17 and 18, the robot  10  rotates about its axis within the transfer chamber  406  to align the wafer handling members  60  with the various chambers  404  attached to the transfer chamber  406 . Once aligned with a chamber  402  and  404 , the robot arms  42  extend, by relative rotation of the first and second struts,  44  and  45 , moving the wafer handling members  60  and the wafers  302  resting thereon into the chamber  404  for transfer. To facilitate faster transfer of the wafers  302  between the chambers  404 , the wafers  302  are clamped on the wafer handling members  60  when resting thereon. The clamp wrist  80  used to facilitate this clamping operates as follows. While the following description refers to only a single robot arm  42 , clamp wrist  80 , and workpiece handling blade  64  for ease of description, it should be understood that operation of dual blades occurs in the same manner at each blade. 
     During wafer transfer on the wafer handling member  60 , the spring, or other biasing member  114  biases a common linkage member  98 , which in turn biases the clamp fingers  90 ,  690  into the clamping position. Only when a sufficient force is applied to the spring, or other biasing member,  114 , will the attached clamp fingers  90 ,  690 , move outward and away from the wafer  302 . Any number of clamp fingers  690  may be provided on the distal end of the blade  64 . Preferably, two clamp fingers  690  are used, which preferably pivot with respect to the blade  64  to allow rotation of the rollers  692  attached thereto towards and away from the wafer  302  in response to axial movement of linkage member  98 . 
     As the robot arms  42  extend into the chamber  404  to complete the transfer between the robot  10  and the chamber  404 , the struts,  44  and  45 , rotate relative to the workpiece handling member  60 . This rotation of the second strut  45  causes a relative rotation of the translational member  82  fixedly attached thereto. The translational member  82  is positioned and adapted so that, when the second strut  45  reaches a predetermined degree of rotation which translates to a given extension of the robot arms  42 , the roller  84  attached to the apogee end of the translational member  82  contacts the contact pad  122  of the first lever  120  causing a pivot of the first lever  120  on continued extension of the robot arm  42 . Accordingly, the translational member  82  translates the extending motion of the robot arm  42 , and the rotational motion of the struts,  44  and  45 , into a rearward rotation of the first lever  120 . The translational member  125  of the first lever  120  then engages the contact pad  135  of linkage member  98 , which also biases the linkage member  98  rearward. As the linkage member  98  is moved rearward, it causes the operatively engaged contact fingers  90 ,  690  to move away from the wafer  302  and the handling blade  64 . The wafer  302  may then be removed from the wafer handling blade  64 . The subsequent retraction of the robot arms  42  causes the translational member  82  to disengage the first lever  120 , and allow the spring, or other biasing member,  114  to return the clamp fingers  90 ,  690  to the clamped position and causing the clamp fingers  90  to engage the edge of the wafer  302  resting on the wafer handling blade  64 , thereby pressing the wafer  302  against the retaining member  70 . 
     In operation of the embodiment shown in FIGS. 19-22, the robot  10  rotates about its axis within the transfer chamber  406  to align the wafer handling members  60  with the various chambers  404  attached to the transfer chamber  406 . Once aligned with a chamber  402  and  404 , the robot arms  42  extend, by relative rotation of the first and second struts,  44  and  45 , moving the wafer handling members  60  and the wafers  302  resting thereon into the chamber  404  for transfer. To facilitate faster transfer of the wafers  302  between the chambers  404 , the wafers  302  are clamped on the wafer handling members  60  when resting thereon. The clamp wrist  80  used to facilitate this clamping operates as follows. While the following description refers to only a single robot arm  42 , clamp wrist  80 , and workpiece handling blade  64  for ease of description, it should be understood that operation of dual blades occurs in the same manner at each blade. 
     During wafer transfer on the wafer handling member  60 , the flexure assembly  500  biases the clamp fingers  90 , into the clamping position shown in FIGS. 20 and 22. The pneumatic cylinder  600  is actuated using a solenoid (not shown) operably connected to a fluid pressure source (not shown) upon extension of the robot arm. Upon actuation of the solenoid, compressed air is fed into the cylinder  600 . When compressed air is fed into the cylinder  600 , the piston retracts, pulling the yoke  510  and the entire flexure assembly  510  rearward away from the wafer  302 . Because the flexure member  114  is fixedly attached to the housing  199 , as the flexure assembly  500  is withdrawn from the wafer  302 , the tip ends, or jaws,  94  are moved rearward and also outward to rotate outward and rearward away from the edge of the wafer  302  (as shown in FIGS.  19  and  21 ). This motion of the jaws  94  facilitates lateral capture of an improperly aligned wafer  302 . When the compressed air supply is cut off, the jaws  94  return to the original position, capturing the wafer (as shown in FIGS.  20  and  22 ). 
     Actuation of the pneumatic cylinder  600  is provided by the robotic control system when it is determined by use of standard sensors well known in the art that the robot arms are in the fully extended position. Preferably, an electronic control signal is provided by the robotic control system to the solenoid (not shown) to open a fluid control valve (not shown) in-line with the fluid pressure conduit  630  operatively connected to the pneumatic cylinder  600 . The remote operation and electronic control of pneumatic cylinders such as pneumatic cylinder  600  is well known in the art. Upon partial withdrawal of the robot arms from the fully extended position, the control system preferably provides an electronic control signal to the solenoid (not shown) to close the fluid control valve (not shown) in-line with the fluid pressure conduit  630 . Upon removal of fluid pressure from the pneumatic cylinder  600 , the flexure assembly is returned to the clamped position, as described hereinabove. 
     The operation of pneumatic cylinders is well known in the art. Generally, the pneumatic cylinder includes a piston within a housing with chambers defined within the housing on opposing sides of the piston. The piston rod is connected to the piston and extends from the housing. It should be noted that the fluid pressure source may preferably be a source of compressed air, in which event the air may be provided to the chamber proximate the piston rod. Alternatively, the fluid pressure source may be a vacuum source, in which event the vacuum pressure may be provided to the chamber opposite the piston rod. Alternatively, the pneumatic cylinder is a hydraulic cylinder in operable connection with a source of hydraulic fluid pressure. 
     While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims which follow.