Abstract:
The present invention is directed to a wafer clamping mechanism responsive to fluid pressure to retain wafers on a surface with minimal clamping force. The clamping mechanism houses simple operative elements within a housing proximate the wafer and can utilize existing fluid pressure sources to energize the clamping mechanism. In a first embodiment, the clamping mechanism includes a piston and cylinder to urge a clamping arm against the wafer in response to fluid pressure. In a second embodiment, the clamping mechanism includes a bellows arrangement for urging the clamping finger against the wafer in response to a fluid pressure source. In a third embodiment, the clamping mechanism includes a bladder arrangement wherein a bladder is expanded using fluid pressure to urge the clamping arm against the wafer in response to a fluid pressure source. In a fourth embodiment, the clamping mechanism includes a flexure member attached to a dual bellows arrangement for urging the flexure member against the wafer in response to a vacuum pressure source. In a fifth embodiment, the clamping mechanism includes a bent flexure member attached to a dual bellows arrangement with an internal piston and cylinder for urging the flexure member against the wafer in response to positive pressure source.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a workpiece handling device, and more particularly, to a hydraulically or pneumatically operated mechanical wafer clamp for securing a substrate to a substrate handling device in a processing system. 
     2. Background of the Invention 
     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 and etch chambers. The combination of chambers in a cluster tool, as well as the operating conditions and parameters under which those 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 them 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 moved to another cluster tool or stand alone tool, such as a chemical mechanical polisher, for further processing. 
     Typical cluster tools process one substrate at a time by passing the substrate through a series of process chambers that are each designed to process a single substrate at a time. However, more recent designs have incorporated a parallel processing structure whereby two substrates are processed at a time. In these dual systems, the robot has a pair of spaced parallel blades that pass the wafers through a series of parallel 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. On exemplary fabrication system is the cluster tool shown in U.S. patent application Ser. No. 08/752,471, entitled “Dual Blade Robot,” filed on Nov. 18, 1996, now U.S. Pat. No. 5,838,121 and which is incorporated herein by reference. 
     Substrate throughput in a cluster tool can be improved by increasing the speed of the wafer handling robot positioned in the transfer chamber. 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 the wafer, the chamber and/or the robot. Further, sliding movements of the substrate on the wafer blade may create contaminants, which if received on a substrate, can contaminate the substrate and the devices formed thereon. 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. 
     Conventional robot designs rely on frictional forces that are present between the bottom surface of a wafer and the top surface of the wafer blade to prevent slippage of the wafer. The robot blade typically includes a wafer bridge on the distal end of the wafer blade and on the base of the blade to confine the wafer between the two ends of the blade. However, the wafer bridge at both the base and the distal end do not extend around the sides of the blade, and therefore, do very little to prevent the wafer from slipping laterally on the blade. Furthermore, the wafers are not always perfectly positioned against the bridge and movement or high rotational speeds may throw the wafer against one of the bridges and cause damage to the wafer or cause the wafer to slip over the bridge and/or off the blade. The total resistance due to friction is easily exceeded by the inertia of the wafer during rapid rotation or extension of the robot. However, this low coefficient of friction is typically relied upon when determining the speed at which a robot rotates. 
     patent application Ser. No. 08/801,076, entitled “Mechanically Clamping Robot Wrist,” filed on Feb. 14, 1997, now U.S. Pat. No. 5,955,858 which is hereby incorporated by reference, further discusses the problem of wafer slippage on a robot blade and provides a mechanical clamping device to secure a wafer to the blade. The mechanical device relies on springs or flexure assemblies to clamp a wafer on a blade and is actuated by relative movement between the arms forming the linkage of the robot. While this is one solution, the design requires a relatively complex assembly to achieve clamping of a wafer. 
     Therefore, there is a need for a workpiece handling device which utilizes a simple and cost-effective wafer handling clamp to secure wafers during movement in a processing system. 
     SUMMARY OF THE INVENTION 
     The present invention is generally directed to a wafer clamping mechanism for retaining a wafer on a wafer handling robot. In one aspect, the wafer clamping mechanism comprises an actuation assembly mounted to the wafer handling robot proximate the wafer seat and a remote fluid source coupled to the actuation assembly through a fluid conduit for engaging the actuation assembly. The actuation assembly is adapted to engage a wafer with radial clamping forces on at least a portion of the edge of the wafer. 
     In one aspect, the clamping mechanism may be a fluid cylinder clamping mechanism, which itself further comprises: a fluid cylinder within a housing of the actuation assembly in fluid communication with the source of fluid pressure; a piston disposed within and adapted to reciprocate within the fluid cylinder in response to fluid pressure within the fluid cylinder; a piston rod affixed to and extending from the piston in a direction generally towards the wafer; and a clamping arm affixed to the housing and normally biased generally away from the wafer. In this aspect, the rod may be adapted to engage the clamping arm and bias the clamping arm towards the wafer to exert radial clamping forces on the wafer upon reciprocation of the piston. The wafer is retained with a clamping force sufficient to retain the wafer but insufficient to deform the wafer. 
     In another aspect, the clamping mechanism may be a bladder clamping mechanism comprising a chamber formed in the housing body of the actuation assembly; a bladder disposed within the chamber and in fluid communication with the source of fluid pressure; and a clamping arm affixed to the housing body and normally biased generally away from the wafer. In this aspect, the bladder is adapted to engage the clamping arm and to bias the clamping arm towards the wafer to exert radial clamping forces when the bladder is expanded or inflated in response to fluid pressure. The wafer is retained with a clamping force sufficient to retain the wafer but insufficient to deform the wafer. 
     In yet another aspect, the clamping mechanism may be a bellows clamping mechanism which comprises a chamber within a housing body of the actuation assembly; a clamping arm affixed to the housing and normally biased generally away from the wafer; and a bellows disposed in and affixed to the housing body chamber and having a front volume in fluid communication with the source of fluid pressure. In this aspect, the bellows has a piston affixed to an end of the bellows generally towards the clamping arm. The bellows piston is adapted to reciprocate within the housing chamber in response to fluid pressure within the front volume within the bellows and to engage the clamping arm and to bias the clamping arm towards the wafer to exert radial clamping forces on the wafer upon reciprocation of the bellows piston. The wafer is retained with a clamping force sufficient to retain the wafer but insufficient to deform the wafer. 
     In still another aspect, the clamping mechanism comprises a dual bellows leaf spring clamping mechanism having a manifold having a fluid passageway therein; a first bellows affixed to the manifold and having a bellows chamber in fluid communication with the manifold passageway; a second bellows affixed to the manifold and having a bellows chamber in fluid communication with the manifold passageway; and a flexure member attached to one or more bellows actuation plates affixed to opposing ends of the first and second bellows. In this aspect, the flexure member forms an arc in a direction generally towards the wafer. The flexure member is also normally biased outward to extend the first and second bellows away from the manifold so that an apogee portion of the flexure member is withdrawn away from the wafer. The bellows actuation plates are further adapted to retract towards the housing in response to fluid pressure provided in the housing to extend the apogee portion of the flexure member in a direction generally towards the wafer to exert radial clamping forces on the wafer. In this aspect, the source of fluid pressure may be a vacuum pressure source and the flexure member may be a leaf spring. 
     In another aspect, the invention provides a method of retaining and releasing a wafer on a wafer handling robot. The method comprises the steps of providing a clamping mechanism proximate an outer edge of the wafer responsive to fluid pressure; providing fluid pressure to the clamping mechanism so that a clamping arm extends towards the edge of the wafer to be retained; and releasing the wafer by removing fluid pressure from the clamping mechanism so that the clamping arm retracts from the edge of the wafer. In this aspect of the invention, the wafer is retained with a clamping force sufficient to retain the wafer but insufficient to deform the wafer. 
    
    
     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 schematic diagram of a first integrated cluster tool incorporating an embodiment of the wafer clamping mechanism of the present invention on a single-blade “frog-leg type” robot. 
     FIG. 2 is a schematic diagram of a second integrated cluster tool incorporating an embodiment of the wafer clamping mechanism of the present invention on a dual-blade “frog-leg type” robot. 
     FIG. 3 is a schematic diagram of a third embodiment of the wafer clamping mechanism of the present invention on a polar robot. 
     FIG. 4 is a partial top view of a workpiece handling member shown in the retracted, engaged, position in connection with the “frog-leg type” robot of FIG.  1 . 
     FIG. 5 is a partial cross-sectional view of the workpiece handling member of FIG. 4 taken along line  5 — 5 . 
     FIG. 6 is partial top view of a workpiece handling member shown in the extended, disengaged, position in connection with the “frog-leg type” robot of FIG.  1 . 
     FIG. 7 is a partial cross-sectional view of the workpiece handling member of FIG. 6 taken along line  7 — 7 . 
     FIG. 8 is a partial top view of a workpiece handling member with a dual-clamping embodiment of the clamping mechanism of the present invention. The workpiece handling member is shown in the extended, disengaged position with the clamping arm and clamping finger withdrawn away from the edge of wafer. 
     FIG. 9 is a partial top view of a workpiece handling member with a dual-clamping embodiment of the clamping mechanism of the present invention. The workpiece handling member is shown in the retracted, engaged position with the clamping arm and clamping finger extended and urged against the edge of the wafer. 
     FIG. 10 is a partial top view of a dual-clamping embodiment of the clamping mechanism shown in connection with the “polar type” robot having a single wafer handling blade. The robot and robot arms are shown in the extended position for delivery or retrieval of a wafer on the wafer blade. 
     FIG. 11 is a partial top view of a dual-clamping embodiment of the clamping mechanism shown in connection with the “polar type” robot having a single wafer handling blade. The robot and robot arms are shown in the retracted position for rotation of the robot with the wafer clamped securely to the wafer blade. 
     FIG. 12 is a cross-sectional view of a first embodiment of a clamping device in accordance with the present invention shown in a neutral, released position. 
     FIG. 13 is a cross-sectional view of a first embodiment of a clamping device in accordance with the present invention shown in an engaged, or retaining position. 
     FIG. 14 is a cross-sectional view of a second embodiment of a clamping device in accordance with the present invention shown in a neutral, released position. 
     FIG. 15 is a cross-sectional view of a second embodiment of a clamping device in accordance with the present invention shown in an engaged, or retaining position. 
     FIG. 16 is a cross-sectional view of a third embodiment of a clamping device to in accordance with the present invention shown in a neutral, released position. 
     FIG. 17 is a cross-sectional view of a third embodiment of a clamping device in accordance with the present invention shown in an engaged, or retaining position. 
     FIG. 18 is a partial top view of a workpiece handling member shown in the extended, disengaged position in connection with the “frog-leg type” robot of FIG.  1 . 
     FIG. 19 is a partial top view of a workpiece handling member shown in the extended, disengaged position in connection with the “frog-leg type” robot of FIG.  18  and also showing a cross-sectional view of a primary, vacuum pressure embodiment of the dual bellows leaf spring clamping mechanism in the disengaged position. 
     FIG. 20 is a partial top view of a workpiece handling member of FIG. 22 shown in the retracted, engaged position in connection with the “frog-leg type” robot of FIG.  18 . 
     FIG. 21 is a partial top view of a workpiece handling member shown in the retracted, engaged position in connection with the “frog-leg type” robot of FIG.  18  and also showing a cross-sectional view of a primary, vacuum pressure embodiment of the dual bellows leaf spring clamping mechanism in the engaged position. 
     FIG. 22 is a partial top view of a workpiece handling member shown in the extended, disengaged position in connection with the “frog-leg type” robot of FIG.  18  and also showing a cross-sectional view of a secondary, positive pressure embodiment of the dual bellows leaf spring clamping mechanism in the disengaged position. 
     FIG. 23 is a partial top view of a workpiece handling member shown in the retracted, engaged position in connection with the “frog-leg type” robot of FIG.  18  and also showing a cross-sectional of a secondary, positive pressure embodiment of the dual bellows leaf spring clamping mechanism in the engaged position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention generally provides an improved wafer clamping mechanism for retaining a wafer on the blade of a wafer handling robot in a vacuum processing system as shown generally in FIGS. 1-3. More particularly, the present invention comprises a robot clamp wrist  80  for mechanically clamping a wafer  302  (or other workpiece) to a wafer handling member  60  mounted on robot arms  42 . Referring to FIG. 2, the present invention may also comprise a dual-wafer robot clamp wrist  80  for mechanically clamping a pair of wafers  302  (or other workpieces) to a pair of wafer handling members  60  mounted on robot arms  42 . The clamping wrist selectively applies sufficient force to prevent wafer slippage and wafer damage during rapid rotation and linear movement of the blade  64  while allowing transfer of the wafer  302  to be accomplished following extension. The clamping wrist biases the wafer  302  on the blade  64  against a retaining member  70  during a specified range of arm extension and/or retraction. 
     In the embodiments shown in FIGS. 1-3, the clamping wrist uses a single clamping mechanism for each blade to position and hold the wafer  302  with minimal particle generation and wafer damage. However, as described further below, two or more clamping mechanisms may be used in connection with each blade  64  to more securely position and hold the wafer  302  on the blade  64 . The clamping mechanism is designed so that wafers  302  are normally clamped except when the wafer blade  64  is near full extension while delivering or picking up a wafer  302 . However, because the chambers may be positioned at different distances from the axis of the robot ( 10 ,  20 ,  30 , respectively, as shown in FIGS.  1 - 3 ), the clamp is designed to release the wafer  302  in a predetermined range of extension to accommodate any discrepancy in delivery distance. 
     FIG. 1 shows a schematic diagram of an exemplary integrated cluster tool  400  useful for processing wafers  302 . Wafers  302  are introduced into and withdrawn from the cluster tool  400  through a loadlock chamber  402 , typically an integral part of tool  400 . A “frog-leg type” robot  10  having a single wafer handling blade  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 the retracted position for rotating freely within the transfer chamber  406  and are also illustrated in phantom in the extended position for retrieving or delivering the wafers within a particular process chamber  404 . The specific configuration of the cluster tool in FIG. 1 is merely illustrative and the system shown is capable of processing a single wafer  302  at a time. However, the invention is equally applicable to other robot assemblies. 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 shows a schematic diagram of another exemplary integrated cluster tool  500  useful for processing wafers  302  in tandem. Wafers  302  are introduced into and withdrawn from the cluster tool  500  through a loadlock chamber  502 , typically an integral part of tool  500 . A dual-blade “frog-leg type” robot  20  having a pair of wafer handling blades  64  is located within the cluster tool  500  to transfer the substrates between the loadlock chamber  502  and the various process chambers  504 . The robot arms  42  are illustrated in the retracted position for rotating freely within the transfer chamber  506  and are also illustrated in phantom in the extended position for retrieving or delivering the wafers within a particular chamber, such as loadlock chamber  502 . 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 a time. However, the invention is equally applicable to other robot assemblies. 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  20 . 
     FIG. 3 shows a “polar type” robot  30  having a single wafer handling blade  64  to transfer the substrates between a loadlock chamber and the various process chambers. The robot arms  42  are illustrated in the retracted position for rotating freely within the transfer chamber  406  and are also illustrated in phantom in an extended position for retrieving or delivering a wafer within a particular process chamber  404 . The specific configuration of the cluster tool in FIG. 1 is merely illustrative and the system shown is capable of processing a single wafer  302  at a time. However, the invention is equally applicable to other robot assemblies having, for example, a dual-blade robot clamp wrist. 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  30 . 
     Now with reference to FIGS. 1-3, each of the robots  10 ,  20 ,  30  include at least one pneumatically actuated wafer clamping mechanism  100  mounted on or otherwise associated with clamp wrist  80 . The wafer clamping mechanism  100  is actuated using existing power source lines. Existing vacuum pressure lines, positive pressure lines, or hydraulic pressure lines may be used or separate fluid pressure lines may be provided to actuate the wafer clamping mechanism  100 . When actuated, wafer clamping mechanism  100  either retains or releases the wafer  302  on the wafer blade  64 , depending on the particular design utilized as described further below. 
     Wafer blade  64  includes a retaining member  70 , which may be a unitary bridge or individual retaining members  70  (as shown) extending upwardly from the distal end of the wafer blade  64  opposite the clamp wrist  80 , and is adapted to abut a wafer  302  disposed on the blade  64 . Wafer clamping mechanism  100  generally retains the wafer  302  on wafer blade  64  by urging the wafer  302  located at the end of the wafer blade  64  proximate the clamp wrist  80  towards and against retaining member  70 . While the wafer is in the retracted position, the wafer clamping mechanism  100  is either actuated or do-actuated (again, depending on the particular embodiment employed) to engage the mechanism  100  to securely retain the wafer  302  on the wafer blade  64 . While the wafer arm is in the fully extended position (shown in phantom), the wafer clamping mechanism  100  is either actuated or de-actuated (again, depending on the particular embodiment employed) to disengage the mechanism  100  to permit the wafer  302  to rest freely on the wafer blade  64  so that it may be removed by conventional methods. 
     FIG. 4 shows a partial top view of workpiece handling member  60  shown in connection with the “frog-leg type” robot having a single wafer handling blade  64 . The robot and robot arms  42  are shown in the retracted position for rotation of the robot. Wafer clamping mechanism  100  is shown mounted on clamp wrist  80  in an engaged position, thus securing the wafer  302  against retaining member  70  (shown in FIG.  1 ). Although not shown, it will be obvious to one of ordinary skill in the art that wafer clamping mechanism  100  may be similarly mounted to the dual-blade “frog-leg type” robot  20  proximate each of the pair of wafer handling blades  64  of robot  20  (shown in FIG.  2 ). 
     FIG. 5 shows a partial cross-sectional view of workpiece handling member  60  taken along line  5 — 5  of FIG. 4 in the engaged position. FIG. 5 shows wrist housing  80  with housing cover plate  81 , which receives and partially contains robot arms  42 . Wafer clamping mechanism  100  is shown mounted on wrist housing  80 . Wafer clamping mechanism  100  includes a clamping arm mounting plate  101  mounted to or integral with the top of body  102  of the mechanism  100 . Clamping arm mounting plate  101  preferably includes a hinge portion  123  from which a clamping arm  110  extends downward and slightly away from the body  102  of clamping mechanism  100 . Hinge portion  123  may preferably be a flexure member which may yield to permit outward movement of the clamping arm  110  to engage the edge of wafer  302 . Alternatively, hinge portion  123  is rigid and clamping arm  110  is a flexure member which may, itself, flex to permit outward movement of clamping finger  111  provided at a distal end of clamping arm  110  proximate the edge of wafer  302 . Upon engagement, face  112  of clamping finger  111  contacts the edge of wafer  302  to abut wafer  302  and urge wafer  302  against retaining member  70  (shown in FIG.  1 ). Clamping arm  110  is shown extending partially within a slot  65  provided in wafer blade  64  so that the face  112  of clamping finger  111  may adequately abut the edge of wafer  302 . 
     FIG. 6 shows a partial top view of workpiece handling member  60  shown in connection with the “frog-leg type” robot having a single wafer handling blade  64 . Robot  10  and robot arms  42  are shown in the extended position for delivery or receipt of a wafer  302 . Wafer clamping mechanism  100  is shown in a disengaged position, thus allowing wafer  302  to rest freely on wafer blade  64  for removal therefrom or placement thereon of a wafer  302 . 
     FIG. 7 shows a partial cross-sectional view of workpiece handling member  60  taken along line  7 — 7  of FIG. 6 in the disengaged position. The hinge portion  123  or clamping arm  110 , depending on the embodiment used, has returned clamping arm  110  and clamping finger  111  to the disengaged position away from the wafer  302  within slot  65 . 
     FIG. 8 shows a dual-clamping embodiment of workpiece handling member  60  in which a pair of wafer clamping mechanisms  100  are provided spaced-apart on the clamp wrist  80  to engage and abut wafer  302  at spaced-apart locations along the periphery of wafer  302 . FIG. 8 shows the dual-clamping embodiment in the extended, disengaged position with the clamping arm  110  and clamping finger  111  withdrawn away from the edge of wafer  302 . As shown, face  112  of clamping finger  111  may preferably have a profile matching the edge of wafer  302  to more securely retain wafer  302 . Although not shown, the entire clamping mechanism  100  may be mounted such that the direction of travel of the clamping arm  110  is co-extensive with a line extending radially outward from the center of the wafer  302  to beneficially align the face  112  of clamping finger  111  with the edge of wafer  302 . FIG. 9 shows the dual-clamping embodiment of workpiece handling member  60  in the retracted, engaged position with the clamping arm  110  and clamping finger  111  abutting the edge of wafer  302  to retain the wafer  302  against retaining member  70  (shown in FIG.  1 ). 
     FIG. 10 shows a partial top view of a dual-clamping embodiment of workpiece handling member  60  shown in connection with the “polar type” robot  30  having a single wafer handling blade  64  (shown in FIG.  3 ). The robot and robot arms  42  are shown in the extended position. A pair of wafer clamping mechanisms  100  are shown mounted directly to and spaced-apart on clamp wrist  80  in a disengaged position permitting removal of a wafer  302  from or placement of a wafer  302  on wafer blade  64 . Wafer clamping mechanisms  100  are shown spaced-apart similar to the embodiment shown in FIGS. 8-9. FIG. 11 shows a partial top view of the dual-clamping embodiment in an engaged position in which the clamping mechanisms firmly secure the wafer  302  to blade  64  as previously described for rotation of the robot  10 . Preferably, in each embodiment, the wafer clamping mechanisms  100  are engaged and/or disengaged simultaneously to beneficially secure the wafer  302  on blade  64 . 
     Fluid Cylinder Clamping Embodiment 
     Referring to FIGS. 12-13, in accordance with a first embodiment of the clamping mechanism  100  of the present invention, the wafer clamping mechanism  100  is preferably a pneumatic cylinder clamping mechanism  600 . The operating mechanisms of pneumatic cylinder clamping mechanism  600  are preferably contained within a housing body  102  without the need of complex linkage mechanisms remote from the mechanism, which would otherwise be exposed to the atmosphere proximate the wafer. Accordingly, particle generation may be minimized to prevent contamination of the wafer through actuation of the wafer clamping mechanism. 
     Fluid cylinder clamping mechanism  600  includes an actuation assembly  120  for providing actuating forces in response to an increase in fluid pressure provided to cylinder bore  130  by an external fluid pressure source (not shown). Actuation assembly  120  includes cylinder bore  130 , defined within the body  102  of actuation assembly  120 . Fluid pressure is provided to cylinder bore  130  through control line  140  in fluid communication with both the cylinder bore  130  and the source of fluid pressure (not shown). 
     Actuation assembly  120  further includes slidable piston  150 , slidably disposed within cylinder bore  130 . A front volume  131  is defined by the body  102 , a front piston face  151  of piston  150 , and a front end cap  113  mounted to body  102 . A back volume  132  is defined by the body  102  and a back piston face  153  of piston  150 . Piston  150  is adapted to be sealingly engaged about the walls of the body  102  and to reciprocate within cylinder bore  130  in response to fluid pressure provided within the front volume  131  of cylinder bore  130 . Accordingly, as fluid pressure is increased within the front volume  131  of cylinder bore  130 , piston  150  is actuated towards the wafer  302 . 
     Actuation assembly  120  further includes a piston rod  152  connected to a rear face  153  of piston  150 . The piston rod  152  extends perpendicularly from the back face  153  outward and through an aperture  122  formed in the body  102 . In operation, the piston rod  152  translates the movement of piston  150  to actuate clamping arm  110  and is suitably sized to contact clamping arm  110  during actuation of the fluid cylinder clamping mechanism  600 . 
     Clamping arm  110  preferably extends outwardly and downwardly from an upper portion of housing  102  and has a clamping finger  111  at a distal end of the clamping arm  110  for engagement with the wafer  302  when the clamping arm  110  has been actuated by actuation assembly  120 . At a proximal end of the clamping arm  110  is attached a semi-rigid biasing shoulder  123 , which in a particular embodiment is an integral component of the clamping arm  110 . The shoulder  123  is sufficiently flexible to allow a biasing force on the clamping arm  110  to actuate the clamping arm  110  away from the body  102  and sufficiently rigid to allow the clamping arm  110  to return to a neutral position (shown in FIG. 12) when the actuating force is removed. Fluid cylinder clamping mechanism  600  is shown in FIG. 12 in a neutral, disengaged position in which clamping arm  110  does not contact the edge  303  of wafer  302 . Clamping arm  110  is, accordingly, shown in its neutral, disengaged position in which it is biased generally towards the housing body  102  and away from the wafer  302 . A clamping distance  65  is provided between the clamping finger  111  and the edge  303  of the wafer  302  in the disengaged position shown in FIG. 12 whereby the clamping finger  111  does not contact the edge  303  of the wafer  302 . In the disengaged position, a wafer  302  may be placed on or removed from the blade  64 . 
     FIG. 13 shows fluid cylinder clamping mechanism  600  in its engaged position in which clamping finger  111  is engaged with the edge  303  of wafer  302  to retain wafer  302  on the wafer handling robot. Accordingly, clamping arm  110  and clamping finger  111  have closed clamping distance  65  so that clamping finger  111  contacts the edge  303  of wafer  302 , thereby retaining wafer  302  on the wafer handling robot  10 ,  20 ,  30  (shown in FIGS. 1-3) with radial clamping forces only at the edge  303  of the wafer  302 . No forces are exerted on either upper or lower surfaces of the wafer. The clamping force is sufficient to retain wafer  302  without deforming wafer  302 . 
     In operation, as fluid pressure is provided through conduit  114  to increase the fluid pressure within cylinder bore  130 , piston  150  is moved towards wafer  302 . As piston  150  moves towards the edge  303  of wafer  302 , piston rod  152  also moves towards the edge  303  of wafer  302 . As piston rod  152  moves towards the edge  303  of wafer  302 , it contacts clamping arm  110  and exerts an actuation force against clamping arm  110 . The actuation force against clamping arm  110  causes clamping arm  110  to flex outwardly away from the housing body  102  and towards the edge  303  of wafer  302  at a shoulder  123  proximate the location where the clamping arm  110  extends from the housing body  102 . As clamping arm  110  flexes away from housing body  102 , it resists the actuation force from the rod  152  and acts as a leaf spring or other biasing member, thereby returning to the neutral or disengaged position when the actuation force is removed as rod  152  is withdrawn away from the clamping arm  110 . To release the wafer  302  from engagement by the clamping arm  110  and thereby the clamping finger  111 , fluid pressure is vented from cylinder bore  130  through conduit  140  or some other means. As fluid pressure is vented from within cylinder bore  130 , the biasing force of clamping arm  110  will continue to act on piston rod  152  and piston  150 . Because piston  150  is not actuated by the fluid pressure in cylinder  130  when fluid pressure is removed from cylinder bore  130 , the biasing force of clamping arm  110  will act against rod  152  and cause piston rod  152  and piston  150  to move away from the edge  303  of wafer  302  and within the body  102 , thereby releasing wafer  302 . 
     It should be noted that the fluid cylinder clamping mechanism  600  shown is initially in a disengaged position at rest when no fluid pressure is provided in the front volume  131 . However, it will be obvious to one of ordinary skill in the art to modify fluid cylinder clamping mechanism  600  so that the fluid cylinder clamping mechanism  600  is maintained in an engaged position when no fluid pressure is provided in the front volume  131 . Although not shown, such modifications could include providing a spring or other biasing member in front volume  131  to overcome the inward bias of clamping arm  110  and to initially bias piston rod  152  against clamping arm  110 . In such a modified embodiment, negative pressure such as provided by a vacuum pressure source in communication with conduit  140  could energize the assembly  120  and disengage the fluid cylinder clamping mechanism  600 . Releasing the vacuum pressure would then permit the biasing member within front volume  131  to again engage the clamping finger  111  of clamping arm  110  against wafer  302 . The same modifications could permit engagement of the assembly  120  by actuation with positive pressure provided in the back volume  132  of assembly  120 . Releasing the positive pressure would thereby permit the spring or other biasing member to overcome the inward bias of clamping arm  110  to engage clamping finger  111  against wafer  302 . 
     Bellows Clamping Embodiment 
     Referring to FIGS. 14-15, in accordance with a second embodiment of the invention, the wafer clamping mechanism is preferably a bellows clamping mechanism  700 . Bellows clamping mechanism  700  is preferably mounted to the wafer handling robot arm proximate the wafer  302  so that the operating mechanisms are contained within its housing body  102  without the need for complex linkage mechanisms remote from the wafer  302 , which would otherwise be exposed to the atmosphere proximate the wafer  302 . Accordingly, particle generation may be minimized to limit or prevent contamination of the wafer  302  through actuation of the wafer clamping mechanism. 
     Bellows clamping mechanism  700  preferably includes an actuation assembly  120  for providing actuating forces in response to an increase in fluid pressure provided to front volume  131  by an external fluid pressure source (not shown). In the bellows clamping embodiment  700 , front volume  131  is defined by bellows  133 , a front face  151  of piston  150 , and front end cap  113  mounted to body  102 . Bellows  133  is disposed within the cylinder bore  130  defined by housing body  102 . Fluid pressure is increased within bellows  133  through control line  140  and conduit  114  in fluid communication with both the front volume  131  within bellows  133  and the source of fluid pressure (not shown). 
     Actuation assembly  120  further includes slidable piston  150 , slidably disposed within cylinder bore  130 . In the bellows clamping embodiment shown in FIGS. 1415, piston  150  is not adapted to be sealingly engaged about the walls of the body  102 , but is instead fixedly and sealingly connected to a distal end of bellows  133  within housing body  102 . The opposing end of bellows  133  is fixedly and sealingly attached to the front end cap  113  opposite wafer  302  and clamping arm  110 . Bellows  133  are adapted to permit piston  150  to freely reciprocate within cylinder bore  130  in response to a fluid pressure increase in the front volume  131  within bellows  133 . Accordingly, as fluid pressure is increased within the front volume  131  of cylinder bore  130 , piston  150  is actuated towards the wafer  302 . 
     Actuation assembly  120  further includes a piston rod  152  connected to a back, or rear face  153  of piston  150 . The piston rod  152  extends perpendicularly from the back face  153  outward and through an aperture  122  formed in the body  102 . In operation, the piston rod  152  translates the movement of piston  150  to actuate clamping arm  110  and is suitably sized to contact clamping arm  110  during actuation of the bellows clamping mechanism  700 . 
     Clamping arm  110  preferably extends outwardly and downwardly from an upper portion of housing body  102  and has a clamping finger  111  at a distal end of the clamping arm  110  for engagement with the wafer  302  when the clamping arm  110  has been actuated by actuation assembly  120 . At a proximal end of the clamping arm  110  is attached a semi-rigid biasing shoulder  123 , which in a particular embodiment is an integral component of the clamping arm  110 . The shoulder  123  is sufficiently flexible to allow a biasing force on the clamping arm  110  to actuate the clamping arm  110  away from the body  102  and sufficiently rigid to allow the clamping arm  110  to return to a neutral position (shown in FIG. 14) when the actuating force is removed. Bellows clamping mechanism  700  is shown in FIG. 14 in a neutral, disengaged position in which clamping arm  110  does not contact the edge  303  of wafer  302 . Clamping arm  110  is, accordingly, shown in its neutral, disengaged position in which it is biased generally towards the housing body  102  and away from the wafer  302 . A clamping distance  65  is provided between the clamping finger  111  and the edge  303  of the wafer  302  in the disengaged position shown in FIG. 14 whereby the clamping finger  111  does not contact the edge  303  of the wafer  302 . In the disengaged position, a wafer  302  may be placed on or removed from the blade  64 . 
     A clamping arm mounting plate  101  mounted to body  102  preferably includes a shoulder  123  from which clamping arm  110  extends downward and slightly away from the body  102  of clamping mechanism  100 . Hinge portion  123  may preferably be a flexure member which may yield to permit outward movement of the clamping arm  110  as it is engaged against the edge  303  of wafer  302 . Alternatively, hinge portion  123  is rigid and clamping arm  110  is a flexure member which may, itself, flex to permit outward movement of clamping finger  111  provided at a distal end of clamping arm  110  proximate the edge of wafer  302 . 
     FIG. 15 shows bellows clamping mechanism  700  in its engaged position in which clamping finger  111  is engaged with the edge  303  of wafer  302  to retain wafer  302  on the wafer handling robot. Accordingly, clamping arm  110  and clamping finger  111  have closed clamping distance  65  so that clamping finger  111  contacts the edge  303  of wafer  302 , thereby retaining wafer  302  on the wafer handling robot  10 ,  20 ,  30  (shown in FIGS. 1-3) with radial clamping forces only at the edge  303  of the wafer  302 . No forces are exerted on either upper or lower surfaces of the wafer. The clamping force is sufficient to retain wafer  302  without deforming wafer  302 . 
     In operation, as fluid pressure is provided through conduit  114  to increase the fluid pressure within bellows  133 , piston  150  is moved towards wafer  302 . As piston  150  moves towards the edge  303  of wafer  302 , piston rod  152  also moves towards the edge  303  of wafer  302 . As piston rod  152  moves towards the edge  303  of wafer  302 , it contacts clamping arm  110  and exerts an actuation force against clamping arm  110 . The actuation force against clamping arm  110  causes clamping arm  110  to flex outwardly away from the housing body  102  and towards the edge  303  of wafer  302  at a hinge point  123  proximate the location where the clamping arm  110  extends from the housing body  102 . As clamping arm  110  flexes away from housing body  102 , it resists the actuation force from the rod  152  and acts as a leaf spring or other biasing member, thereby returning to the neutral or disengaged position when the actuation force is removed as rod  152  is withdrawn away from the clamping arm  110 . To release the wafer  302  from engagement by the clamping arm  110  and thereby the clamping finger  111 , fluid pressure is vented from the front volume  131  within bellows  133  through conduit  140  or through another evacuation member. As fluid pressure is vented from within bellows  133 , the biasing force of clamping arm  110  will continue to act on piston rod  152  and piston  150 . Because piston  150  is not actuated by the fluid pressure within bellows  133  when fluid pressure is removed from front volume  131 , the biasing force of clamping arm  110  will act against rod  152  and cause piston rod  152  and piston  150  to move away from the edge  303  of wafer  302  and within the body  102 , thereby releasing wafer  302 . 
     It should be noted that the bellows clamping mechanism  700  shown is initially in a disengaged position at rest when no fluid pressure is provided in the front volume  131 . However, it will be obvious to one of ordinary skill in the art to modify bellows clamping mechanism  700  so that the bellows clamping mechanism  700  is maintained in an engaged position when fluid pressure is not increased within the front volume  131 . Although not shown, such modifications could include providing a spring or other biasing member in front volume  131  to overcome the inward bias of clamping arm  110  and to initially bias piston rod  152  against clamping arm  110 . In such a modified embodiment, negative pressure such as provided by a vacuum pressure source in communication with conduit  140  could energize the assembly  120  and disengage the bellows clamping mechanism  700 . Releasing the vacuum pressure would then permit the biasing member within front volume  131  to again engage the clamping finger  111  of clamping arm  110  against wafer  302 . The same modifications could permit engagement of the assembly  120  by actuation with positive pressure provided in the back volume  132  of assembly  120 . Releasing the positive pressure would thereby permit the spring or other biasing member to overcome the inward bias of clamping arm  110  to engage clamping finger  111  against wafer  302 . Similarly, evacuating back volume  132  of cylinder bore  130  with a vacuum pressure source would increase the pressure within front volume  131  relative to back volume  132 , thereby causing piston  150  to move outward towards clamping arm  110  to engage wafer  302 . 
     Bladder Clamping Embodiment 
     Referring to FIGS. 16-17, in accordance with a third embodiment of clamping mechanism  100  of the present invention, the wafer clamping mechanism  100  is preferably a bladder clamping mechanism  800 . Bladder clamping mechanism  800  is preferably mounted to the wafer handling robot arm proximate the wafer  302  so that the operating mechanisms are contained within its housing body  102  without the need for complex linkage mechanisms remote from the wafer  302 , which would otherwise be exposed to the atmosphere proximate the wafer  302 . Accordingly, particle generation may be minimized to minimize or prevent contamination of the wafer through actuation of the wafer clamping mechanism. 
     Bladder clamping mechanism  800  preferably includes an actuation assembly  120  for providing actuating forces in response to an increase in fluid pressure provided to a front volume  131  within bladder  230  by an external fluid pressure source (not shown). Actuation assembly  120  includes bladder  230 , disposed within a chamber  730  defined by body  102 . Fluid pressure is increased within front volume  131  of bladder  230  through control line  140 , conduit  114  formed in a front end cap  113  of body  102 , and conduit  115  formed in body  102 , each of which is in fluid communication with both the front volume  131  within bladder  230  and the source of fluid pressure (not shown). 
     Bladder  230  is adapted to be disposed within chamber  730  and to inflate and deflate within chamber  730  in response to an increased fluid pressure in the front volume  131  defined by bladder  230  through conduit  140 . Accordingly, as fluid pressure is increased within the front volume  131  of bladder  230 , bladder  230  expands or inflates towards the wafer  302  to actuate clamping arm  110 . Clamping arm  110  may include a shoulder or nipple  252  extending from clamping arm  110  in a direction generally towards bladder  230  to assist in contact between the expanding bladder  230  within chamber  730  to actuate clamping arm  110 . Shoulder  252  preferably extends from clamping arm.  110  and into chamber  730  provided in housing body  102  of the actuation assembly  120  and is suitably sized to contact bladder  230  during actuation of the bladder clamping mechanism  700 . 
     Clamping arm  110  preferably extends outwardly and downwardly from an upper portion of housing  102  and has a clamping finger  111  at a distal end of the clamping arm  110  for engagement with the wafer  302  when the clamping arm  110  has been actuated by actuation assembly  120 . At a proximal end of the clamping arm  110  is attached a semi-rigid biasing shoulder  123 , which in a particular embodiment is an integral component of the clamping arm  110 . The shoulder  123  is sufficiently flexible to allow a biasing force on the clamping arm  110  to actuate the clamping arm  110  away from the body  102  and sufficiently rigid to allow the clamping arm  110  to return to a neutral position (shown in FIG. 16) when the actuating force is removed. Bladder clamping mechanism  800  is shown in FIG. 16 in a neutral, disengaged position in which clamping arm  110  does not contact the edge  303  of wafer  302 . Clamping arm  110  is, accordingly, shown in its neutral, disengaged position in which it is biased generally towards the housing body  102  and away from the wafer  302 . A clamping distance  65  is provided between the clamping finger  111  and the edge  303  of the wafer  302  in the disengaged position shown in FIG. 16 whereby the clamping finger  111  does not contact the edge  303  of the wafer  302 . In the disengaged position, a wafer  302  may be placed on or removed from the blade  64 . 
     FIG. 17 shows bladder clamping mechanism  800  in its engaged position in which clamping finger  111  is engaged with the edge  303  of wafer  302  to retain wafer  302  on the wafer handling robot. Accordingly, clamping arm  110  and clamping finger  111  have closed clamping distance  65  so that clamping finger  111  contacts the edge  303  of wafer  302 , thereby retaining wafer  302  on the wafer handling robot  10 ,  20 ,  30  (shown in FIGS. 1-3) with radial clamping forces only at the edge  303  of the wafer  302 . No forces are exerted on either upper or lower surfaces of the wafer. The clamping force is sufficient to retain wafer  302  without deforming wafer  302 . 
     In operation of the third embodiment  800 , as fluid pressure is increased within front volume  131  within bladder  230 , bladder  230  expands or inflates radially towards wafer  302 . As bladder  230  expands radially towards clamping arm  110 , it contacts clamping arm  110  or shoulder  252  of clamping arm  110 . Shoulder  252  translates the radial expansion of bladder  230  to actuate clamping arm  110  and is suitably sized to contact clamping arm  110  during actuation of the bladder clamping mechanism  800 . The actuation force against clamping arm  110  causes clamping arm  110  to move outwardly away from the housing body  102  and towards the edge  303  of wafer  302 . As clamping arm  110  moves away from housing  102 , it resists the actuation force from the bladder  230  and acts as a leaf spring or other biasing member, thereby returning to the neutral or disengaged position when the actuation force is removed as bladder  230  is deflated and moved away from the clamping arm  110 . To release the wafer  302  from engagement by the clamping arm  110  and thereby the clamping finger  111 , fluid pressure is vented or otherwise decreased within the front volume  131  within bladder  230 . As fluid pressure is decreased within front volume  131  within bladder  230 , the biasing force of clamping arm  110  may continue to act on bladder  230 . Because bladder  230  is not actuated when fluid pressure is removed from bladder  230 , the biasing force of clamping arm  110  may act against bladder  230  to compress bladder  230  or assist in the deflation of bladder  230  within chamber  730 . Accordingly, clamping arm  110  and clamping finger  111  retracts from wafer  302 , thereby releasing wafer  302  and disengaging clamping mechanism  100 . 
     Dual Bellows Leaf Spring Embodiment 
     Referring now to FIGS. 18-21, in accordance with a fourth embodiment of the invention, the wafer clamping mechanism is preferably a dual bellows leaf spring clamping mechanism  900 . Dual bellows leaf spring clamping mechanism  900  is preferably mounted to the wafer handling robot arm proximate the wafer  302  so that the operating mechanisms are contained within a manifold  902  and bellows  930 ,  940  without the need for complex linkage mechanisms remote from the wafer  302 , which would otherwise be exposed to the atmosphere proximate the wafer  302 . Accordingly, particle generation may be minimized to minimize or prevent contamination of the wafer  302  through actuation of the wafer clamping mechanism. 
     Dual bellows leaf spring clamping mechanism  900  preferably includes an actuation assembly  920  for providing actuating forces in response to fluid pressure provided to manifold  902  and thence to bellows  930 ,  940  by an external fluid pressure source (not shown). Actuation assembly  920  includes a first bellows  930  and a second bellows  940  sealingly engaged on opposing sides of manifold  902 . First and second bellows  930 ,  940  each define bellows chambers  931 ,  932  (Shown in FIGS.  19  and  21 ), respectively, in fluid communication with a passageway  905  defined within the manifold  902  of actuation assembly  920 , which is described in further detail below. 
     Actuation assembly  920  further includes a first bellows actuation member  950  connected to a distal end of first bellows  930  and a second bellows actuation plate  960  connected to a distal end of second bellows  940 . Proximal ends of bellows  930 ,  940  are fixedly and sealingly attached to opposing walls of manifold  902 . Bellows  930 ,  940  preferably extend in opposite directions in a plane co-extensive with wafer  302 . Bellows  930 ,  940  are adapted to permit bellows actuation plates  950 ,  960  to freely reciprocate in response to fluid pressure within the chambers  931 ,  932  of bellows  930 ,  940 , respectively. 
     Opposing ends of a flexure member such as leaf spring  910 , which may be stainless steel, are fixedly attached to both bellows actuation plates  950 ,  960 , and are flexed in an arc between the actuation plates  950 ,  960  on a side of the manifold  902  generally towards the wafer  302 . Accordingly, the leaf spring  910  is held in place in a plane co-extensive with the wafer  302 . As shown in FIGS. 18 and 19, leaf spring  910  is normally biased outwardly away from the manifold  902  so that apogee portion  911  is normally retracted generally away from the wafer  302 . Accordingly, as leaf spring  910  attempts to straighten according to its normal bias, bellows  930 ,  940  are extended from the manifold  902  in opposing directions. As shown in FIGS. 20 and 21, as bellows  930 ,  940  are retracted towards manifold  902 , leaf spring  910  is further bent away from its normal bias and apogee portion  911  of leaf spring  910  moves towards wafer  302  to retain wafer  302  on the wafer handling robot. A clamping distance  65  is provided between the leaf spring  910  and the wafer  302  when the leaf spring  910  is in its neutral, retracted, position as shown in FIGS. 18 and 19. 
     FIG. 18 shows a partial top view of workpiece handling member  60  shown in connection with the “frog-leg type” robot having a single wafer handling blade  64 . The robot  10  and robot arms  42  are shown in the extended position for delivery or receipt of a wafer  302 . Spring clamping mechanism  900  is shown mounted on clamp wrist  80  in a disengaged position, thus allowing wafer  302  to rest freely on wafer blade  64  for removal therefrom or placement of a wafer  302  thereon. Although not shown, it will be obvious to one of ordinary skill in the art that wafer clamping mechanism  900  may be similarly mounted to the dual-blade robot. 
     FIG. 20 shows a partial top view of workpiece handling member  60  shown in connection with the “frog-leg type” robot having a single wafer handling blade  64 . The robot arms  42  are shown in the retracted position for rotation of the robot  10 . Wafer clamping mechanism  900  is shown mounted on clamp wrist  80  in an engaged position, thus securing the wafer  302  against retaining member  70  (shown in FIG.  1 ). Although not shown, it will be obvious to one of ordinary skill in the art that wafer clamping mechanism  900  may be similarly mounted to the dual-blade robot. 
     FIGS. 19 and 21 show a detailed partial cut-away view of workpiece handling member  60  in the disengaged position of FIG.  18  and the engaged position of FIG. 20, respectively. FIGS. 19 and 21 show wrist housing  80 , which is operatively connected to robot arms  42 . Bellows  930 ,  940  define and enclose bellows chambers  931 ,  932 . Manifold  902  includes a fluid passageway  905  which communicates fluid pressure provided through conduit  140  to both of the bellows chambers  931 ,  932  of bellows  930 ,  940 , respectively. 
     Within bellows chambers  931  and extending in opposing directions generally outward away from manifold  902  are first and second cylinders  903 ,  904 . Cylinders  903 ,  904  are adapted to receive actuation plate extensions  952 ,  954 , extending generally inward toward manifold  902  from actuation plates  950 ,  960 , respectively. Cylinders  903 ,  904  and extensions  952 ,  954  provide a telescoping support mechanism to assist in maintaining generally axial movement of actuation plates  950 ,  960  away from manifold  902  as actuation plates  950 ,  960  reciprocate to retract and extend bellows  930 ,  940 , thereby respectively engaging spring  910  with and disengaging spring  910  from wafer  302 . In the primary embodiment  900  shown in FIGS. 19 and 21, bellows  930 ,  940  are initially at a resting, disengaged position when spring clamping mechanism  900  is not energized. However, in an alternative embodiment  980  described below with reference to FIGS. 22 and 23, the resting position may engage the clamping mechanism and the wafer is, instead, disengaged by energizing the spring clamping mechanism. 
     FIGS. 19 and 21 respectively show a partial cut-away view of the spring clamping mechanism  900  in the initial, resting position of FIG. 18 in which the mechanism is disengaged and in the engaged position of FIG.  20 . With reference to FIG. 19, bellows  930 ,  940  are expanded by the biasing force of spring  910  and the spring  910  is withdrawn from the edge  303  of wafer  302 . Bellows  930 ,  940  are retracted to urge spring  910  against the edge  303  of wafer  302  by decreasing the fluid pressure within bellows chambers  931 ,  932 . A vacuum pressure source is provided in communication with conduit  140  and passageway  905  to at least partially evacuate the volume within bellows chambers  931  and  932 . As the bellows chambers  931 ,  932  are evacuated, bellows  930 ,  940  and actuation plates  950 ,  960  are retracted to further flex spring  910 , which urges the apogee portion  911  of spring  910  against the edge  303  of wafer  302  as shown in FIG.  21 . As spring  910  is urged against wafer  302 , wafer  302  is urged against retaining member  70  provided at the distal end of wafer blade  64  (shown in FIGS.  1 ). 
     FIGS. 22 and 23 show partial cut-away views of an alternative embodiment of spring clamping mechanism  980  in the disengaged and engaged positions, respectively. The secondary embodiment  980  is energized using a positive fluid pressure source (not shown) instead of the vacuum source used in the primary embodiment  900  to energize the clamping mechanism. Like the primary embodiment  900 , secondary embodiment  980  is at rest initially in the disengaged position shown in FIG. 22 with spring  910  retracted away from the wafer  302 . As shown in FIG. 23, when energized by the fluid pressure source, the mechanism  980  is engaged to urge the spring  910  against wafer  302 . A cylinder  981 ,  982  is provided within each of bellows chambers  931 ,  932  and is sealingly mounted to manifold  902 . Cylinders  981 ,  982  receive pistons  983 ,  984  extending from actuation plate extension  950 ,  960  and include sealing members  986  to permit the piston to reciprocate within cylinders  981 ,  982  while providing sealing engagement between bellows chambers  931 ,  932  and cylinder bores  987 ,  988  defined by inner walls of cylinder  981 ,  982 . Passageways  970 ,  971  are provided in cylinders  981 ,  982  to provide fluid communication between manifold passageway  905  and cylinder bores  987 ,  988 . 
     Pistons  983 ,  984  each include a sealing member  989  around the periphery thereof to define a first volume  992 ,  993  between the sealing member  989 , the cylinder bore  987 ,  988 , and the sealing member  986 . Second volume  994 ,  995  is similarly defined between the sealing member  986 , the cylinder bore  987 ,  988 , and manifold  902 . Passageways  970 ,  971  provide fluid communication between the first volume  992 ,  993  and passageway  905  of manifold  902  so that fluid pressure provided through conduit  140  is communicated to first volume  992 ,  993 . 
     Engagement and disengagement of wafer  302  by spring  910  and the corresponding outward and inward movements of actuation plates  950 ,  960  are similar to the primary embodiment  900 . The operational difference between the two embodiments is in the manner of energizing the mechanism. In the alternative embodiment  980 , positive fluid pressure is provided through conduit  140 , manifold passageway  905 , and cylinder passageways  970 ,  971  to the first volume  992 ,  993  within each of the bellows  930 ,  940 , respectively. An increase in fluid pressure within first volumes  992 ,  993  causes pistons  983 ,  984  and actuation plates  950 ,  960  attached thereto to reciprocate inward toward manifold  902 . Accordingly as described above in connection with the primary embodiment  900 , spring  910  is flexed to urge apogee portion  911  outward to engage wafer  302 . Removing the pressure source from conduit  140  decreases the pressure in first volume  992 ,  993 . The biasing force from spring  910  again returns pistons  983 ,  984  to an outward position, and apogee portion  911  of spring  910  withdraws away from wafer  302  to release wafer  302  from engagement within the clamping mechanism  980 . 
     While the foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims which follow.