Abstract:
Presented is an end-effector for grasping integrated circuit wafers with a talon-like device that effectively grips an arcuate peripheral “free zone” of the wafer-without effecting contact of the wafer in a manner to contaminate it. Structurally, in one aspect of the invention, the end-effector or talon-like device is formed by-confronting top and bottom plate members configured to form a “shell” within which is displaceably mounted a member which, when selectively displaced in one direction by the imposition-of-an-appropriate force, opens a normally-closed gripping member for receiving the arcuate peripheral “free zone” of the wafer and when selectively displaced in the opposite direction by the removal of the opening force tightly grips the arcuate peripheral “free zone” of the wafer to releasably retain it attached to the end-effector, from which it may selectively be released by the imposition of force in an opening direction that opposes and overcomes the force that effects gripping of the wafer. An indicator may be provided to signal the proper positioning of the wafer in relation to the end-effector, and a control system may be provided to effect opening and closing operation of the arcuate talon-like clamp.

Description:
BACKGROUND OF THE INVENTION 
     In the manufacture of integrated circuit wafers and other devices, such as disks for CDs and computer hard disk drives, methods and apparatus have been developed for effecting the manufacture of the integrated circuit wafers and other devices in ultra-clean environments as free as possible from any source of contamination that might adhere to the semiconductor wafer or other such devices. It has been found that these essentially sterile conditions can best be achieved by manufacturing these devices, including IC wafers, in “clean rooms” where semiconductor-wafers of various sizes, e.g., 4,6, 8 and 12 in. in diameter are processed, these devices and wafers having various thicknesses averaging about 0.030″ and being flat to very close tolerances. In the case of semiconductor wafers, each contains a multiplicity of independent integrated circuits or “chips” embedded therein, and the wafers are preferably handled in their wafer-form to efficiently effect the mass production and testing of the independent integrated circuits imbedded therein. 
     It is in this handling and manipulation of the completed wafers or other devices where the specter of contamination from an outside source frequently arises. Ideally, each wafer or other device would be moved or transferred from one location to another, during manufacture and thereafter, without having its top or bottom surfaces touched by any means, human or mechanical, this to prevent contamination of the top and bottom surfaces of the wafer. Accordingly, one of the principal objects of the present invention is the provision of a method and apparatus or device that may be selectively attached to and detached from an integrated circuit wafer or other device without contaminating the sensitive active areas of the surfaces of the wafer or other device. 
     One of the conventional methods for handling integrated circuit wafers is the use of an “end-effecter” that comprises an arm attached at its proximal end to a robotic manipulation mechanism and the source of negative pressure, i.e., a vacuum source. A channel is formed in the end defector, with the proximal end of the channel communicating with the vacuum source while the distal end of the channel opens onto a top surface on or near the distal end of the arm that abuts against the bottom side of the wafer, the wafer thus being et “sucked” or drawn against the top surface of the end-effector by the negative or “vacuum” pressure imposed on the bottom surface of the wafer. Much development effort has been expended to develop various types of structures that utilize this method of attachment of a manipulation arm or “end-defector” to the underside of an integrated circuit wafer, and numerous patents have issued illustrating and describing these types of devices. A sampling of these types of patent is as follows: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 4,627,151 
                 4,720,130 
                 4,778,332 
               
               
                   
                 4,923,054 
                 5,395,198 
                 5,556,147 
               
               
                   
                   
               
             
          
         
       
     
     However, such development efforts have not overcome the fact that the top surface of the end-effector that touches the wafer, top or bottom surface, may itself be contaminated and that such contamination may be transferred to the wafer. Another disadvantage of the vacuum clamping type of end-effecter wafer handling system is the risk of an interruption of the vacuum pumping system resulting from a power failure or a vacuum system leak that could cause disengagement of the wafer from the end-effector with consequent loss of the wafer through displacement laterally or vertically, with attendant striking of adjacent structures by the wafer, resulting in chipping or shattering of the wafer. 
     Much development effort has been expended to mitigate the disadvantages of end-effectors that utilize vacuum engagement end-effectors, and this development effort has generally been directed to the design of devices that operate by grasping the wafer in a manner to impose radially directed forces on the circumferential peripheral edge of the wafer, i.e., forces imposed in a direction perpendicular to the central axis of the wafer. A sampling of devices utilizing this method of grasping a wafer may be found in the following United States patents: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 4,410,209 
                 4,586,743 
                 4,715,637 
               
               
                   
                 4,717,190 
                 5,133,635 
                 5,474,641 
               
               
                   
                 5,810,935 
                   
                 5,851,041 
               
               
                   
                   
               
             
          
         
       
     
     The patents listed above have resulted from a preliminary patentability and novelty search, and it appears that all of these patents are directed to the concept of the imposition of a radially inwardly directed force on the circumferential peripheral edge of the wafer. 
     Accordingly, another principal object of the present invention is the provision of a method and apparatus for gripping or grasping of an arcuate “free-zone” extending radially inwardly from a peripheral edge of a wafer by the imposition of a gripping force directed perpendicularly to the flat surface of the wafer or, stated in other words, by a gripping force imposed on an arcuate peripheral “fee-zone” surface portion of the wafer in a direction parallel to the central axis of the wafer, i.e., perpendicular to the “free-zone” surface portion of the wafer. 
     Another object to the present invention is the provision of an end-effector that eliminates the use of negative pressure or “vacuum” to engage itself to an integrated circuit wafer via surface contact as occurs with end-effectors that utilize the vacuum engagement principle and instead utilizes positive or negative pressure to activate a mechanism that grasps or releases the wafer in a non-active arcuate peripheral “Free-zone” or area. 
     A still further object of the invention is the provision of an end-defector device that utilizes fail-safe positive pressure to effect selective clamping or release of a wafer gripped by the end effecter so that the WAFER remains gripped by the end effecter even in the event of equipment failure. 
     Integrated circuit wafers may intentionally be manufactured with a “non-intrusion” area surrounded by a peripheral “free zone” of selected width of about 2 mm that is not occupied by it or used for the formation of integrated circuits in the wafer. It is important that this peripheral “free-zone” be as narrow as possible so as to maximize the number of integrated circuits that are formed in the “non-intrusion” area of the wafer. 
     Accordingly, it is yet another object of the invention to provide an end-effecter operable to selectively grip a wafer by the deployment of a gripping device on the peripheral “free-zone” of the wafer and the imposition of a sufficient gripping force applied perpendicularly to the top and bottom surfaces in the “free-zone” to prevent inadvertent release of the wafer while responding to positioning commands and which remains responsive to selectively applicable positive or negative fluid pressure to cause or cancel the positive gripping force to thus selectively grip or release the wafer. 
     A still further object of the invention is the provision of an end-defector device incorporating means for selectively gripping and releasing a substantial arcuate surface portion of the peripheral “free-zone” of an integrated circuit wafer on both top and bottom surfaces of the wafer surrounding the “non-intrusion” area and without intrusion into the “non-intrusion” area. 
     A still further object of the invention is the provision of an end-effector device for reliably gripping and effecting manipulation of an integrated circuit wafer without contact with the “non-intrusion” surface areas of the wafer, and comprising a selectively adjustable arcuate socket for receiving the arcuate “free-zone” of an integrated circuit wafer, the socket being actuable to an open condition for insertion of the wafer “free-zone” thereinto, and thereafter being actuable to resiliently grip or clamp onto the arcuate “free-zone” portion of the wafer to retain it gripped by the socket until selectively released therefrom. 
     A still further object of the invention is the provision of an end-effector device that is operable to selectively grip the arcuate peripheral “free-zone” of the wafer at circumferentially spaced locations thereon. 
     Yet another object of the invention is the provision of an end-effector device controllable manually or automatically by a control system responsive to input from sensors to effect opening of the socket to receive an arcuate peripheral “free-zone” of the wafer and to effect closing adjustment or clamping of the socket on the peripheral “free-zone” when the arcuate peripheral “free-zone” is properly inserted and seated in the socket. 
     The invention possesses other objects and features of advantage, some which, with the foregoing, will become apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiments illustrated and described since it may be embodied in various forms within the scope of the appended claims. 
     SUMMARY OF THE INVENTION 
     In terms of broad inclusion, the end-effector of the invention for grasping integrated circuit wafers comprises a talon-like device that effectively grips resiliently or otherwise, an arcuate peripheral “free-zone” of the wafer to enable risk-free manipulation of the wafer in whatever direction is appropriate and without effecting contact of the wafer in a manner to contaminate it. The end-effector of the invention may selectively be used in opposed pairs to grip large wafers by their diametrically opposed arcuate peripheral “free-zones” or, preferably, may be used individually to grip a single arcuate peripheral “free-zone” of a wafer. Structurally, in one aspect of the invention, the end-effector or talon-like device is formed by two confronting top and bottom plate members configured to form a “shell” within which or between which is displaceably mounted a member which, when selectively displaced in one direction by the imposition of an appropriate force, opens a normally closed gripping member for receiving the arcuate peripheral “free-zone” of the wafer and when selectively displaced in the opposite direction by the removal of the opening force tightly grips the arcuate peripheral “free-zone” of the wafer to releasably retain it attached to the end-effector, from which it may selectively be released by the imposition of force in an opening direction that opposes and overcomes the force that effects gripping of the wafer. It will of course be understood that the end-effector may be configured as a normally open device that is closed, i.e., by an appropriately directed force. Appropriate sensors, while not essential, are preferably provided to signal the proper positioning of the wafer in relation to the end-effector, and a control system may be provided responsive to the sensor signals to effect opening and closing operation of the arcuate talon-like socket or clamp. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of the end-effector of the invention shown in its position of non-intrusive gripping attachment to a peripheral “free-zone” of a wafer. 
     FIG. 2 is a top plan view of the end-effector of the invention apart from a wafer and equipped with an adaptor for connection of the end-effector to a conventional robotic control system. 
     FIG. 3 is a bottom plan view of the monolithic top plate of the end-effector separated from the bottom plate and other components and illustrating the detailed construction of the interior of the top plate. 
     FIG. 4 is a top plan view of the monolithic bottom plate of the end-effector separated from the top plate and other components and illustrating the detailed construction of the interior of the bottom plate. 
     FIG. 5 is a top plan view of the interior of the bottom plate of the end-effector as shown in FIG. 4 but with a selectively actuable pressure actuated displacement assembly mounted therein. 
     FIG. 6 is a top plan view of the selectively actuable pressure actuated displacement assembly shown apart from other structure. 
     FIG. 7 is a top plan view similar to FIG.  5  and illustrating wafer peripheral edge gripping means mounted on the bottom plate and including a plurality of resiliently displaceable beams or tines extending radially across the selectively actuable pressure actuated displacement assembly. 
     FIG. 8 is an enlarged top plan view of a wafer peripheral edge gripping means shown apart from other structure. 
     FIG. 9 is a vertical cross-sectional view taken in the plane indicated by the line  9 - 9  in FIG.  8 . 
     FIG. 10 is an enlarged bottom plan view of the wafer peripheral edge gripping means illustrated in FIG.  8  and shown apart from other structure. 
     FIG. 11 is an enlarged vertical cross-sectional view taken in then plane indicated by the line  11 - 11  in FIG. 1 illustrating a spring pressure activated normally closed fail-safe end-effector embodiment illustrating the relationship of the components when the bladder is inflated so as to open the end-effector to receive a wafer. A portion of the wafer is shown in broken lines. 
     FIG. 12 is an enlarged vertical cross-sectional view taken in the same plane as FIG. 11 but showing the bladder deflated to cause the spring-pressed wafer receptor jaws of the end-effector to close and resiliently grasp the “free-zone” acruate edge portion of the wafer in a fail-safe manner through the imposition of retention forces applied perpendicular to the top and bottom surfaces of the wafer. 
     FIG. 13 is an enlarged vertical cross-sectional view taken in the same plane as FIG. 11 but illustrating a spring pressure activated normally open end-effector device in which the deflated but selectively inflatable bladder is positioned to effect clamping closure of the end-effector jaws upon the arcuate peripheral edge “free-zone” area of the wafer when the bladder is inflated and release therefrom when the bladder is deflated as shown. 
     FIG. 14 is an enlarged vertical cross-sectional view similar to FIG. 13, but showing the bladder inflated and the arcuate peripheral edge portion of the wafer surrounding the “non-intrusion” area clampingly grasped by the end-effector. 
     FIG. 15 is a top plan view of a specially configured mounting bracket adapted to be detachably interposed between the end-effector of the invention and an associated specific conventional robotic equipment. The specially configured portion of the bracket is shown in broken lines. 
     FIG. 16 is an edge view of the mounting bracket viewed in the direction of the arrow  16  in FIG.  15 . 
     FIG. 17 is a perspective view illustrating in general the configuration of a third embodiment wafer “free-zone” gripping and vacuum-driven fail-safe end-effector. 
     FIG. 18 is a perspective view similar to FIG. 17 of a fourth embodiment wafer “fee-zone” gripping and vacuum-driven “standard”, i.e., non-fail-safe end-effector. 
     FIG. 19 is a diagrammatic plan view of the bottom plate of the end-effector illustrated in FIG. 17, showing the relationship of a number of the individual clamps that are vacuum-driven to grip the wafer “free-zone” in a fail-safe or “standard” non-fail-safe manner. 
     FIG. 20 is a view similar to FIG. 19, but illustrating a lesser number of wafer-gripping clamps associated with the “free-zone” of a smaller diameter wafer. 
     FIG. 21 is a view similar to FIG. 19, but illustrating a lesser number of wafer-gripping clamps associated with the “free-zone” of a still smaller wafer. 
     FIG. 22 is a view similar to FIG. 19, but illustrating only three wafer-gripping clamps associated with the “free-zone” of a still smaller wafer. 
     FIG. 23 is a diagrammatic view of the diaphragm and normally-closed wafer-gripping clamps shown apart from other structure for clarity, and showing the clamps in a normally closed fail-safe arrangement. 
     FIG. 24 is a diagrammatic vertical cross-sectional view illustrating the diaphragm and a normally-closed wafer-gripping clamp mounted on the bottom plate of an end-effector shown apart from the top plate. 
     FIG. 25 is a plan view of one of the wafer “free-zone” gripping clamps shown apart from other structure 
     FIG. 26 is an edge view of the clamp of FIG. 25 taken in the direction of the arrow  26  in FIG.  25 . 
     FIG. 27 is a plan view of one of the mounting pistons adapted for mounting on the top surface of the diaphragm and on which the wafer-gripping clamp shown in FIGS. 25 AND 26 is adapted to be pivotally mounted. 
     FIG.  27 (A) is an end elevational view of the mounting piston illustrated in FIG. 27 taken in the direction of arrow  27 (A). 
     FIG. 28 is a plan view of a spring plate adapted to be mounted on the bottom surface of the diaphragm in conjunction with the mounting piston shown in FIG.  27 . 
     FIG.  28 (A) is an edge view of the spring plate illustrated in FIG. 28, taken in the direction of the arrow  28 (A). 
     FIG. 29 is a perspective view shown in exploded form and illustrating the positional relationships of the diaphragm, the mounting piston, the spring plate and a normally-closed or normally-open wafer-gripping clamp with a portion of the bottom plate of the fail-safe or “standard” end-effector. 
     FIG. 30 is a fragmentary exploded view partly in vertical cross-section illustrating the positional relationships of the components of FIG. 29 embodying a normally-closed wafer clamping arm. A portion of the flange perimeter of the diaphragm is broken away for clarity. 
     FIG. 31 is a vertical cross-sectional view through a fail-safe end-effector assembly arranged with a spring-pressed normally-closed wafer-clamping member adapted to be opened by drawing a vacuum in the chamber below the diaphragm. 
     FIG. 32 is a vertical cross-sectional view through a standard normally-open end-effector assembly intended as a replacement for conventional end-effectors that vacuum-clamp a wafer, this assembly being spring-pressed into an open condition and clamped to a wafer by drawing a vacuum min the chamber below the diaphragm. 
     FIG. 33 is a vertical cross-sectional view of a slightly modified spring-pressed normally open end-effector adapted to be closed by drawing a vacuum in the chamber below the diaphragm. 
     FIG. 34 is a diagrammatic view of the three normally-open single pole switching assembly that provides positioning data to the logic circuit which in turn controls the LEDs that indicate functional conditions on the end-effector. 
     FIGS. 35A-35C are schematics of the end-effector control system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 through 14, and specifically to FIG. 1 of the drawings, it will be noted that the end-effector designated generally by the numeral  2  is associated with a circular integrated circuit wafer designated generally by the numeral  3 . The integrated circuit wafer  3  is provided with a “non-intrusion” circular area on its top surface  4  that extends radially outwardly from the center  6  of the wafer to a circular perimeter designated generally by the numeral  7 . The circular perimeter  7  defines the area on the face of the wafer on which are embedded the individual integrated circuits in the structure of the wafer. The perimeter  7  that defines the “non-intrusion” area of the wafer lies approximately 2 mm or 0.0787″ from the outer periphery  8  of the wafer. It is the primary purpose of the end-effector of this invention to grasp the wafer only in the annular area defined between the outer periphery  8  of the wafer and the outer perimeter  7  of the “non-intrusion” area of the wafer within which the integrated circuits are contained. By restricting gripping of the wafer by the end-effector  2  to an acruate portion of this annular band of approximately 2 mm, it will be seen that there is only a miniscule or no possibility that the surface of the wafer will be contaminated by the end-effector since no portion of the end-effector comes into contact with the “non-intrusion” surface area of the top and bottom of the wafer. 
     As stated above in the objects of the invention, the end-effector  2  is operative to selectively grip or grasp or clamp onto a finite arcuate portion of this narrow annular band with such tenacity and gripping force exerted perpendicular to the surface  4  of the wafer and parallel to the central axis of the wafer that the wafer may be transported by the end-effector at any velocity that imposes up to three times the force of gravity, or more, in any attitude in which the wafer may be moved from one position to a second position, or under appropriate robotic control, in which the wafer may be flipped from a horizontal attitude into a vertical attitude or vice versa, and similarly the wafer may be moved by robotic control in a circular path to reposition the wafer for whatever purpose is necessary during the manufacturing and testing process for the wafer. 
     To accomplish this end, i.e., to enable maneuverability of the end-effector to grip the wafer only in an arcuate peripheral portion of the annular “free-zone” of the wafer without encroachment into the “non-intrusion” area  4  of the wafer, the end-effector  2  is preferably mounted on a robotic mechanism for accurate placement equipp 3 d as shown in FIG. 2 with a bracket designated generally by the numeral  9  and illustrated in FIGS. 2,  15  and  16 . 
     In FIGS. 2,  15  and  16 , the portion of the bracket shown in broken lines provides the ability to mount the end-effector on an already existing specific robotic mechanism of limited accessability. This portion of the bracket would be omitted from all standard end-effectors adapted to be mounted on most conventional robotic mechanisms. 
     For a better understanding of the means by which such grasping or gripping of a wafer by an end-effector is accomplished, reference is made to FIGS. 2 and 14, where, specifically in FIG. 2, there is illustrated a top plan view of an end-effector  2  formed in an arcuate configuration to provide a circularly arcuate leading edge  13 , circularly arcuate rear edges  14  and  16  separated by a radially extending mounting extension  17  integral with the top plate  12  and which will be described in greater detail with reference to detailed illustrations of the top plate in FIG.  3 . Additionally, the circularly arcuate top plate  12  is provided with end edges  18  and  19  and it will be seen that a robotic adaptor  9  is attached to the radially extending integral portion  17  of the top plate to facilitate mounting of the end-effector on conventional existing robotic mechanisms (not shown). 
     Referring to FIG. 3, this view illustrates the top plate  12  flipped over or inverted so as to illustrate the construction of the plate when viewed from its underside. As there shown, the underside of the top plate  12 , which has by way of example a nominal thickness of approximately 2 mm but may be thinner or thicker as the need prescribes, is milled to provide an elongated recess  21  extending longitudinally of the radially extending mounting portion  17  of the top plate, being equidistant from opposite side edges and milled or otherwise formed into the bottom surface  22  of the top plate to provide an end wall  23  and parallel side walls  24  and  26 . As shown in FIG. 3, the side walls  24  and  26  of the recess  21  extend downwardly where they are intercepted by end edges  27  and  28 , respectively, which lie opposite end edges  29  and  31  which with the end edges  27  and  28  define laterally extending passageways between the interior of the recess  21  and the laterally and circularly extending arcuate recesses  32  and  33  which also may be milled or otherwise formed in the bottom surface of the top plate  12 . 
     It should be noted that within the recess  21 , there is formed a central beam designated generally by the numeral  34  and having an end edge  36  intercepted by side edges  37  and  38  that extend to adjacent an end wall  39  formed in laterally spaced pad portions  41  and  42 . It should be noted that short of the end wall  39 , the beam  34  is reduced in height to provide an abutment  43 , resulting in the beam portion  44  below the abutment  43  being of lesser height than the main portion of the beam. It should also be noted that the end edges  27  and  28  that intercept the side edges  24  and  26 , respectively, of the recess  21 , are themselves intercepted by angularly diverging edges  46  and  47  that are intercepted, respectively, by the edges  48  and  49  of passageways  51  and  52 , each of which communicate, respectively, with recesses  53  and  54 . The purpose of these recesses, and the passageways  51  and  52 , and the passageways defined between the end edges  27 / 29  and  28 / 31  will be explained hereinafter. It should be noted however at this point that the bottom surface  22  of the top plate lies in a common plane with the top surface of the beam  34 , the pads  41  and  42 , and the pads that are defined by the angularly diverging edges  46  and  47 . 
     It should also be noted that the bottom surface  22  of the top plate as illustrated in FIG. 3 lies in the same plane as the arcuate peripheral edge surfaces  56  and  57  which are formed between the outer peripheries  14  and  16  and the inner arcuate peripheries  58  and  59  that define the associated boundaries of the recess  32  and  33 , respectively. The opposite perimeters of the recesses  32  and  33  are defined by the arcuate edges  61  and  62 , which edges are slightly below the plane of the surfaces  22 ,  56  and  57  and the surfaces of the pads  41  and  42 . From the edges  61  and  62  that define the inner peripheral edge of the recesses  32  and  33 , the top plate is chamfered in the area  63  so that a sloping surface is provided between the edges  61 / 62  and the inner peripheral edge  13  of the top plate. 
     At each opposite end of the top plate, adjacent the end edges  18  and  19 , it will be seen that the surface of the top plate is-milled or otherwise formed, as by die-casting or molding, to provide a peninsula designated generally by the numeral  64  associated with the end edge  18 , and a peninsula designated generally by the numeral  66  associated with the end edge  19  of the top plate. Side edges  67  and  68  of the peninsulas define the end edges, respectively, of the recesses  33  and  32 , and with substantially parallel peninsulas  69  and  71 , define passageways  72  and  73 , respectively, into recesses  74  and  76  and passageways  77  and  78  which communicate with the chamfered edge  63  as shown. The purpose of the recesses  74  and  76  and the passageways  72  and  73  thereinto, together with the purpose of the passageways  77  and  78 , will become apparent hereinafter. It is noted at this point however that the recesses  74  and  76  are connected by passageways  82  and  81 , respectively, to the exterior of the end-effector, these passageways terminating or opening onto the chamfered edge  63  in the same manner that the ends of the passageways  77  and  78  terminate in the chamfered edge  63 . In like manner, referring to the recess  44  formed in the beam  34 , it will be noted that a passageway  83  is formed in the top plate to communicate between the recess  44  and the chamfered edge  63 . 
     The end-effector illustrated in FIGS. 1 and 2 includes both a top plate  2  and a bottom plate designated generally by the numeral  86 . These two plates are essentially mirror images of one another, as will be seen from a comparison of FIGS. 3 and 4, with only specific differences between the two plates which will be described in connection with FIG.  4 . However, completing the description of the top plate illustrated in FIG. 3, it is noted that to effect connection of the top plate  2  to the bottom plate  86 , the top plate is provided with a multiplicity of through-bores  87  formed in the extension  17  and in the peripheral edge portions  56  and  57  and in the beam  34  through which mounting screws may be inserted as will hereinafter be explained. In like manner, calling attention to the arcuate inner periphery  13 , it will be noted that spaced radially outwardly from the peripheral edge  13  in both recesses  32  and  33  there are equally spaced four cylindrical studs  88 , each of which is provided with a central through-bore communicating with the top surface of the top plate  12  and through which additional mounting screws may be inserted from the top surface so as to threadably engage complementary threaded bores formed in the bottom plate in which the mounting screws may be engaged as will hereinafter be explained. 
     Referring now to FIG. 4, it will be seen from a comparison with FIG. 3 that the bottom plate corresponds in configuration with the top plate, and that the bores  91  corresponding in position with the bores  87  in the top plate, are in axial alignment with the bores  87  when the two plates are confrontingly superposed one upon the other, with the bores  91  being threaded to receive the threaded shanks of mounting screws  92  (FIG.  1 ). In like manner, the bored studs  88  extending integrally perpendicularly from the bottom of the recesses  32  and  33 , are in axial alignment with the threaded mounting bores formed in similar studs  93  integral with a peripheral portion of the bottom plate and projecting perpendicularly therefrom. 
     The bottom plate  86  illustrated in FIG. 4 is also provided with an elongated recess  94  corresponding in size and position to the recess  21  in the top plate as shown in FIG.  3 . However, in the bottom plate  86 , a through-bore  96  is provided at the end of the recess adjacent the end edge  97  as shown. The purpose of this through-bore will be explained hereinafter. Additionally, while in the top plate the arcuate recesses  32  and  33  are flat in a direction transverse to the edges  58 / 59  and  61 / 62 , respectively, in the bottom plate the recesses  98  and  99 , corresponding to the recesses  32  and  33 , are provided intermediate the defining arcuate edges  101 / 102  and  103 / 104 , with integral elevated arcuate areas  106  and  107  that project a predetermined amount above the bottom surfaces of the recesses  98  and  99 . With respect to the recess  98 , the elevated area  106  is defined along one edge by a raised integral arcuate bead  108  that is parallel and spaced from the associated edge  101  of the recess  98 . 
     In like manner, the elevated integral arcuate area  107  is defined along one edge by a raised integral arcuate bead  109  spaced from and parallel to the inner edge  102  of the recess  99 . As with the top plate structure illustrated in FIG. 3, the bottom plate structure is provided with a radially outwardly projecting mounting extension  112  in which the recess  94  is centrally formed, together with the centrally aligned beam  113  which corresponds in position and dimensions with the beam  34  as illustrated in FIG.  3 . All other aspects of the top plate  2  and the bottom plate  86  are essentially identical. 
     That being the case, it will be seen that when the top plate is superposed over the bottom-plate, the recesses  21  and  94  coincide to form a generally rectangular nacelle for a purpose which will hereinafter be explained. Similarly, the arcuate recesses  32  and  98  coincide to form an arcuate chamber between the top and bottom plates, as do the recesses  33  and  99 . The peninsulas  64  and  66  formed in the top plate similarly coincide with the corresponding peninsulas  64 ′ and  66 ′ formed in the bottom plate, as do the peninsulas  69  and  71  coincide with the complementary peninsulas  69 ′ and  71 ′ formed on the bottom plate. It will thus be understood that passageways  73  and  78  complement similar coinciding passageways  73 ′ and  78 ′ formed in the bottom plate, the passageway  78 ′ communicating with the chamfer  63 ′ , while the passageways  72 ′ and  73 ′ communicate, respectively, with the recesses  74 ′ and  76 ′, which communicate respectively, with the passageways  81 ′ and  82 ′ that terminate in the chamfered area  63 ′ as shown. 
     Referring to FIGS. 5 and 6, it will be seen in FIG. 5 that the interior recesses or nacelles  98  and  99  of the bottom plate as illustrated in FIG. 4, are provided with the assembly designated generally by the numeral  116  and shown in FIG. 6 apart from other structure. The recess  94  (FIG. 4) receives the generally rectangular bifurcated manifold plate  117  provided on its underside with a recess  118  (FIG. 6) that sealingly communicates with the apertures  96  formed in the recess  94  of the bottom plate there illustrated. The manifold plate fits snugly into the recess  94 , and is provided with latterly spaced leg members  119  and  121 , the inner confronting edges of which provide a space  122  therebetween that snugly embraces the elongated beam  113  formed on the bottom plate. 
     Diametrically extending passageways  123  and  124  (FIGS. 5 and 6) formed in the manifold plate communicate with the recesses  118  and  94 , and communicate also with elongated passageways  126  and  127  that extend to near the ends  128  and  129 , respectively, of the leg members  126  and  127 , where they in turn communicate with oppositely extending nipples  131  and  132 , respectively, secured to the side edges of the leg members as shown. Sealingly secured adhesively to the nipples  131  and  132  are inflatable bladders  133  and  134 , respectively, each of the bladders being formed of suitable material to fit on the raised portions  106  and  107  within recess  98  and  99  respectively. 
     As seen in FIGS. 5 and 6, the bladders  133  and  134  are initially flat, sealed at their distal ends  135 , with their proximate ends  135 ′ sealed about and secured to the nipples, so that the interiors of the bladders communicate with the interiors of the nipples so that fluid under pressure may selectively be injected through the aperture  96  and the passageway communicating therewith and into the bladders to effect their inflation and expansion under pressure, and their subsequent deflation when appropriate. In FIG. 5, it will be seen that the deflated bladders  133  and  134  are superimposed, respectively, upon the elevated areas  106  and  107  formed within the recesses  98  and  99 . The bladders lie generally coextensive with the elevated areas, and opposite elongated side edges  136  and  137  of the bladders lie generally parallel to the beads  108  and  109  as seen in FIG.  5 . 
     With the bladder assembly thus mounted on the interior of the bottom plate  86 , a first prefabricated comb-like wafer-clamping or gripping device designated generally by numeral  141  is superimposed over the bladder  133  as shown in FIG. 7, and a second prefabricated comb-like wafer-clamping or gripping device designated generally by the numeral  142  is superimposed over the bladder  134  as also shown in FIG.  7 . The wafer-clamping or gripping devices  141  and  142  are identical to one another and the specific structure of each is illustrated enlarged in FIGS. 8,  9  and  10  for clarity. As there seen, each of the gripping devices constitutes a separate article of manufacture which may be formed by machining or injection molding. 
     Referring to FIGS. 8,  9  and  10 , it will be seen that each clamping device  141  and  142  is arcuate in its configuration, each spanning an arc of approximately 31° and including a channel-shaped edge portion designated generally by the numeral  143 . The channel  143  is formed with a bottom wall  144 , a first side wall  146  and a second side wall  147 . The two side walls are arcuate and spaced sufficiently that when deposited over a bladder as illustrated in FIG. 7, the channel slips snugly into the arcuate space between the inner edges  101  and  102 , as the case may be, and the corresponding associated rib  108  and  109 , each wafer-clamping device thus being detachably retained from inadvertent displacement in any direction. 
     Integrally attached to the second side wall  147  of each of the wafer-clamping devices are a series of ten radially-extending beams, each designated generally by the numeral  148 . While ten wafer-clamping beams are illustrated, it should be understood that the quantity will vary with end-effectors of different sizes. The beams  148  are each integrally attached to the associated second side wall  147  by a flexible or “live” hinge  149  which comprises a narrowed section of the beam having a flat backside  151  (FIGS. 9 and 10) and a curved top or front side  152  in the form of a groove having an arcuate bottom as seen in FIGS. 8 and 9. From the narrowed down flexible “live” hinge portion  149 , each beam extends radially away from the hinge portion and is tapered approximately 3° along its longitudinal edges  153  and  154 , converging toward an end edge  156  that is narrower than the portion  157  that is integral with the “live” hinge  149 . Additionally, it should be noted that the beams are spaced apart approximately 0.031″ so that each of the beams may be independently displaced without affecting the displacement of the adjacent beams. 
     Adjacent its end edge  156 , each of the beams is provided with a recess  158  formed by cylindrical walls  159  closed by a bottom wall  161 . Additionally, to enhance the flexibility of the “live” hinges  149 , there are provided through-holes  162  spaced typically 3° apart and thus shortening the length of the arcuate narrowed flexible “live” hinge portion  149  that integrally yet flexibly attaches each of the beams to the associated second flange  147  of channel member  143 . Thus, collectively, the ten side-by-side beams  148  all lying generally in the same plane, subtend an arcuate angle of approximately 31°, with the radial dimension of each of the wafer-clamping devices being approximately 1.150″ and the length of each individual beam, measured from the second flange  147  to the end edge  156  being approximately 0.950″. The through-holes  162  are conveniently approximately 0.125″ in diameter, while the recesses  158  formed adjacent the end edges  156  of the beams are also conveniently approximately 0.125″ in diameter having cylindrical walls approximately 0.070″ deep. 
     From FIGS. 8 and 10, it will be seen that between the second and third beams  148 , counting from the left in FIGS. 8 and 10, and between the fourth and fifth, and between the sixth and seventh, and between the eighth and ninth beams, there are provided in the adjacent edges of these beams confronting half-circle recesses which define a series of four apertures  163  that are spaced apart and which coincide with the positions of the four bored studs  93  illustrated in FIG. 4, which studs project into the apertures  163  when the wafer-clamping devices are superimposed over the bladders as illustrated in FIG.  7 . 
     Referring to FIGS. 7,  8 ,  9 ,  11  and  12 , it should be noted that the recesses  158  formed in the distal end portions of the beams  148  each accommodates a coiled compression spring  171  that slips loosely into the recess and which has a length sufficient that after insertion into the accommodating recess the top end of the spring projects above the top level or upper surface  172  of the beam on which the spring is supported. Since there are two sets of ten beams  148 , there are of course twenty springs, one for each beam. As a consequence, when the top plate is superimposed over and detachably secured to the bottom plate with the coiled compression springs in position, the top ends of the springs come to bear upon the undersurfaces  32  and  33  of the top plate shown in FIG.  3 . The downwardly projecting bored studs  88  in the top plate are axially aligned with the threaded studs  93  on the bottom plate, thus binding the top plate to the bottom plate and capturing the springs. 
     As a consequence of the elastic resilient force imposed upwardly on the top plate by each of the multiplicity of coiled compression springs, it is seen in FIG. 12 that an equal downward force is imposed by each spring on its associated beam, and each beam  148  is caused by such downwardly directed force to flex downwardly, separating the distal end portion of the beam from the associated inner surface of the top plate and, in the absence of an intervening wafer, bringing the bottom surface  161  of each of the beams adjacent its free end edge  156  into impinging contact with the inner surfaces of the recesses  98  and  99  formed in the bottom plate. 
     Since this relationship of the parts exists in the absence of a wafer when the bladders are deflated, it follows, as illustrated in FIGS. 11 and 12, that when a wafer is in place the very narrow flat surface portion  173  adjacent the end edge  156  of each beam is pressed tightly against the top surface of the wafer in the narrow arcuate band or “free-zone” that surrounds the “non-intrusion” area of the wafer when a wafer is in proper position. Such pressure on the top “free-zone” surface of the wafer causes the complementary bottom arcuate edge portion of the wafer to be pressed tightly against the very narrow flat surface  174  of the bottom plate, as illustrated in FIG.  12 . Thus, when a wafer intervenes and is gripped by each beam, the bottom wall  161  of the beam does not impinge on the inner surface of the bottom plate. 
     It will thus be understood that the “free-zone” of the wafer is tightly gripped between the multiplicity of downwardly pressing beams  148  and the flat narrow arcuate surface of the bottom plate that lies adjacent the chamfered area of the bottom plate  86 . In this embodiment, FIGS. 11 and 12, the wafer is gripped in a fail-safe manner that prevents inadvertent release of the wafer, thus preserving its integrity and obviating the financial loss that would occur if the wafer were to be inadvertently released and fall from the end-effector. 
     To free the wafer from the fail-safe gripping action end-effector as illustrated in FIG. 12, reference is made to FIG. 11 where it is seen that the bladders  133 / 134 , interposed between the bottom plate surfaces  106  and  107  and the underside of the two sets of wafer-clamping devices  141 , when inflated by the admission of an appropriate fluid such as nitrogen through the aperture  96  and into the bladders, causes the bladders to expand and, as shown in FIG. 11, elevate the beams  148  against the pressure exerted on them by the springs  171 . As shown, the springs are compressed, and the end portion  173  of each of the beams is lifted and disengaged from the “free-zone”  7  of the wafer, thus releasing the wafer for appropriate storage in a rack (not shown) or transferred to another processing station for further fabrication procedures or testing. 
     Since the gripping action of the wafer by the end-effector occurs automatically by virtue of the pressure exerted by the springs  171 , and since it is highly unlikely that the bladders would, inadvertently, be inflated, it follows that this embodiment discloses and describes a fail-safe end-effector device for grasping and manipulating a wafer in a non-contaminating manner. It should also be noted that the terms “up”, “down” and “lifted” are relative terms and that the clamp as illustrated in FIGS. 11 and 12 is working down relative to the confronting abutment surface  174  but may also be configured to work upwardly or laterally in relation to an abutment surface. 
     FIGS. 13 and 14 illustrate a second embodiment of the invention in which the bladders must be inflated or pressurized (FIG. 14) to effect gripping of the wafer, with consequent release of the wafer when the bladders are deflated (FIG.  13 ). It will of course be understood that this is a mode of operation that is essentially the reverse of the mode of operation of the embodiment illustrated in FIGS. 11 and 12. To effect this result, in this second embodiment, the springs  171  are interposed between the bottom plate and the underside of the beams  148 , while the bladders are interposed between the top plate and the top surfaces of the beams. Thus, as shown in FIG. 13, deflating the bladders causes the springs  171  to flex the beams upwardly, thus disengaging the flat surface  173  of each beam from the “free-zone” of the associated wafer and thus releasing the wafer to a storage rack or to another processing station. 
     On the other hand, when it is desired to grip a wafer with the end-effector of this embodiment, as shown in FIG. 14, the bladders are inflated by an appropriate fluid such as nitrogen under appropriate pressure and control, causing the distal end portions of the beams  148  to be flexed downwardly against the elastic resilience of the springs  171 , resulting in the springs being compressed as shown, and bringing the undersurface  173  of each beam independently into gripping contact with an arcuate portion of the “free-zone” of the wafer surrounding the “non-intrusion” area of the wafer. It should be noted that this mode of operation, while using positive pressure rather than negative pressure or vacuum, equates with the conventional “standard” vacuum-operated end-effector devices in that if the pressure-generating system in this embodiment fails for any reason, the wafer will be released by the end-effector in the same way that it will be released by a “standard” vacuum-operated surface-clamping end-effector of current technology should the vacuum system fail for any reason. Despite this similarity, one advantage of this pressure operated end-effector is that it eliminates the possibility of contamination of the wafer since its only contact with the wafer is with the “free-zone” surrounding the “non-intrusion” area of the top surface of the wafer and a very narrow peripheral arcuate band of approximately 31° on the underside of the wafer. A second advantage is that the holding force is unlimited and at a minimum is three times (3x) that of the conventional technology. 
     From a structural point of view, it will be noted from FIGS. 13 and 14 that the exterior configuration of the top and bottom plates is the same as in FIGS. 1 and 2, but some changes have been incorporated into the interior of the bottom plate. Thus, with respect to the bottom plate  86 ′ , the elevated areas  106  and  107  seen clearly in FIG. 4 are omitted in this embodiment, and the beams are provided with notch  176  in their top surfaces to accommodate the placement of the bladders  133  and  134 , only bladder  134  being shown in these cross-sectional views. Additionally, the recess  158 ′ in each beam adjacent the end edge  156  is formed in the bottom surface of the beam instead of the top surface so that the springs  171  may be accommodated between the undersides of the beams and the bottom surfaces of the recesses  98  and  99  of the bottom plate. 
     Means are provided on the end-effectors of the first and second embodiments of the invention described above to ensure that the wafer “free-zone”  7  is properly positioned with respect to the gripping surfaces  173  of the beams  148  and the complementary arcuate gripping band  174  of the bottom plate as a condition precedent to the deflation of the bladders in the embodiment of FIGS. 11 and 12, and as a condition precedent to the inflation of the bladders in the embodiment illustrated in FIGS. 13 and 14. 
     Referring to FIGS. 3 and 7, it will be noted that the recesses  74  and  76  formed in the underside of the top plate as seen in FIG. 3 confront similar recesses  74 ′ and  76 ′ formed in a corresponding location on the interior of the bottom plate. It should be borne in mind that the top plate as viewed in FIG. 3 is inverted and that when it is superimposed “right-side-up” over the bottom plate the recesses  74 / 74 ′ and  76 / 76 ′ will be in a confronting relationship. In like manner, the recess  44  formed in the beam  34  of the top plate corresponds in location and dimension to the recess  44 ′ formed in the beam  113  in the bottom plate as seen in FIG.  4 . Passageways  81  and  82  communicate with the recesses  76 / 76 ′ and  74 / 74 ′ and a passageway  83  communicates with the interior of the recess  44  formed in the beam  34 . Micro-switch devices  176 ,  177  and  178  are enclosed within these recesses as illustrated in FIG. 1, and these are connected by appropriate electrical or electronic leads  181 ,  182  that pass from channels  72  and  73  through the channel  143  (FIG. 7) and emerge through the apertures  53  and  54  in the top plate (FIG. 4) to be connected to a source of power and robotics. A fiber optic bundle  183  (FIGS. 11-14) passes through the passageways  77 / 77 ′ and  78 / 78 ′ shown in FIGS. 3-5 and  7  and also continues through the channel  43  formed on each wafer-gripping device as illustrated in FIGS.  7  and  11 - 13 . 
     These micro-switches  176 ,  177  and  178  include plungers that are slidably mounted in passageways  81 / 81 ′ ,  82 / 82 ′ and  83 / 83 ′ and each switch is appropriately connected to a power source and activated when the peripheral edge of the wafer is properly positioned within the end-effector gripping means and depresses the plunger. The fiber optic bundles  183  lead to optical type sensors mounted in the passageways  77  and  78  that “see” and determine when the wafer is present. When present, the switches check to confirm that the wafer is properly seated in the end-effector. In both instances, the leads from the micro-switches and sensing devices terminate in enunciators that indicate either wafer presence or by the illumination of appropriate illuminated signals when the end-effector and wafer are properly related for activation of the wafer-gripping means. Such activation may be carried out automatically by computer-controlled robotic equipment to which the end-effector is connected by means of an appropriate connector terminal mounted on the bracket designated generally by the numeral  184  and illustrated in FIGS. 1,  15  and  16 . 
     Such computer-controlled robotic equipment is conventionally used in the industry and is not part of the invention described and illustrated herein. However, the bracket herein illustrated and described is provided to enable connection of the end-effector of this invention to conventional robotic equipment, thus facilitating implementation of the end-effector of the present invention with conventional robotic equipment already in place in wafer handling equipment. As seen in FIGS. 15 and 16, the bracket  184  comprises two bifurcated opposite end portions designated generally by the numerals  186  and  187 . The larger bifurcated end portion  186  includes a bottom plate  188  spaced from and parallel to an upper plate  189 . A through-bore  191  is provided in the geometric center of the bottom plate  188  for connection to a source of gas under pressure or to a vacuum supply. 
     Third and fourth embodiments of the invention are illustrated in FIGS. 17 and 18 and include in FIG. 17 a perspective view of a fail-safe end-effector and in FIG. 18 an end-effector designated generally by the numeral  202  that is not fail-safe and instead is designated as a “standard” end-effector in that it is readily applicable to existing vacuum systems that are used by conventional end-effectors. These two embodiments of the invention are similar to the end-effectors in the sense that they include gripping means that reliably grip the “free-zone” that surrounds the “non-intrusion” area of the integrated circuit wafer that is sensitive to contamination. Referring to FIG. 17, it will be noted that this fail-safe end-effector  201  is similar to the end-effectors described above in that it includes a top plate  203 , a bottom plate  204 , the top plate  203  being superposed over the bottom plate  204  and secured thereto by appropriate machine screws  206 . Mounted on the top plate is an indicator box  207  having three signal lights designated generally by the numeral  208 , the first light when illuminated indicating that the end-effector is ready to accept a wafer, the second light when illuminated indicating that the wafer is loaded into the end-effector, and properly positioned therein, while the third light when illuminated indicates that the end-effector has been clamped onto the wafer. These functions are indicated by appropriate indicia  209  printed on the top surface of the indicator box. To enable mounting of the end-effector in robotic equipment, the end-effector is provided with a rearwardly extending mounting portion designated generally by the numeral  212  provided with appropriate apertures  213  to which the adaptor bracket illustrated in FIGS. 15 and 16 may be attached. It should be understood that while the indicator box  207  is illustrated and its function explained herein, it is not an essential element of the combination, but is preferred when the end-effectors disclosed herein are robotically controlled. 
     In like manner, and referring to FIG. 18, which depicts the “standard” non-fail-safe type of edge gripping end-effector illustrated in FIGS. 13 and 14, it, too, is provided with an upper plate  213 , a lower plate  214 , the plate  213  being superimposed over the plate  214  and secured thereto by appropriate screws  216 . Mounted on the top plate  213  is a signal box  217  provided with a group of three lights  218 , the first of which, when illuminated indicates that the end-effector is ready to receive a wafer, the second light being illuminated to indicate that the wafer is properly loaded and positioned, while the third light when illuminated indicates that the end-effector has clamped onto the “free-zone” of the wafer. These functions are indicated by appropriate indicia designated by the numeral  219 . As with the end-effector illustrated in FIG. 17, the end-effector of FIG. 18 is also provided with a rearward extension designated generally by the numeral  221  having mounting bores  222  for detachable attachment of the mounting bracket or adaptor illustrated in FIGS. 15 and 16 which facilitates connection of the end-effectors illustrated in FIGS. 17 and 18 to appropriate robotic equipment. 
     As previously described, the end-effectors of this invention are designed to reliably grip the “free-zone” on the peripheral annular portion of a wafer that surrounds the “non-inclusion” portion of the wafer. Since there are different diameters of wafers, generally four inches, six inches, eight inches and twelve inches, the end-effectors of this invention are constructed to accommodate the different diameters of wafers by providing an adequate number of gripping beams for the various wafer sizes. Thus, referring to FIGS. 19 through 21, inclusive, it will be noted that the end-effector illustrated diagrammatically in FIG. 19 is provided symbolically with ten separate wafer clamping or gripping devices or assemblies arranged in an arcuate pattern corresponding to the peripheral arc of the wafer that they are intended to grip. More or fewer wafer clamping devices could be used under appropriate circumstances. In the interest of brevity in this description, each of the wafer gripping assemblies is designated generally by the numeral  226  and it is noted that each is mounted on the bottom plate of the end-effector and is shown in a mounted relationship on a wafer designated generally by the numeral  227 . As described above in connection with other embodiments, the wafer  227  is provided with an annular “free-zone”  228  that measures approximately 0.080″ radially inwardly from the outer periphery of the wafer, such “free-zone” being the area on the top surface of the wafer that is grasped by the individual gripping assemblies  226  when the end-effector is clamped onto the wafer. 
     With respect to the end-effector illustrated in FIG. 20, it is noted that in this case the end-effector is applied to a wafer  299  that is nominally eight inches in diameter, thus requiring a shorter include angle to accommodate sufficient gripping or clamping assemblies  226  to adequately grip and reliably support the smaller diameter wafer. As indicated in FIG. 20, this size end-effector symbolically utilizes six of the individual wafer gripping assemblies, again arranged in an arcuate pattern as illustrated. 
     Referring to FIG. 21, it will be noted that in this case, the end-effector again has been reduced in size to accommodate the reduction in size of the nominally six inch diameter wafer  231  by application symbolically of only four independent wafer gripping assemblies  226 . It should be understood that the independent gripping assemblies  226  are mounted on the bottom plate of the end-effector as illustrated, and that the end-effector and the included gripping assemblies  226  are arranged so as to receive and grip the peripheral annular “free-zone” edge portion of the wafer in a reliable manner. 
     Referring to FIG. 22, it will here be seen that the wafer  232  is nominally a four inch diameter wafer and that it is attached to the end-effector by the gripping action provided symbolically by three cooperatively associated gripping or clamping assemblies  226  mounted on the bottom plate of the end-effector. 
     Referring to FIGS. 23 and 33, it will be seen that the internal construction of each of the end-effectors incorporates the gripping assemblies in such a manner that a given end-effector may be normally closed and opened by the application of vacuum or negative pressure to the end-effector, thus operating in a “fail-safe” mode, (FIGS.  24  and  31 ), or they may be arranged in a normally open configuration wherein a vacuum or negative pressure must be applied to the end-effector to effect gripping operation of each of the gripping assemblies as seen in FIGS. 32 and 33, thus operating in a non-fail-safe mode. 
     Referring to FIGS. 25 through 30, the detailed construction of each of the wafer gripping assemblies, including the various components that make up the assembly, are illustrated as separate components, and as exploded views illustrating the positional relationships of the components one to the other. Thus, referring to FIGS. 25 and 26, each of the gripping assemblies  226  includes a clamp arm designated generally by the numeral  236  and comprises a generally T-shaped structure including a stem portion  237  formed integrally with the cross-bar designated generally by the numeral  238 . This component  236  is preferably fabricated from metal, the stem  237  having transversely extending thickened portion  239  and  241  as illustrated in FIG. 26, to accommodate transversely extending bores  242  and  243  for a purpose which will hereinafter be explained. The cross-bar  38  is provided with slots  244  generally evenly spaced across the length of the bar  238  to provide four segments  246  that are integral with the cross-bar  238  as shown, and which penetrate the cross-bar for a distance of approximately 0.100″ which is approximately one-half the width of the cross-bar  238 . It should also be noted that the edges  247  of the cross-bar are arranged in an arcuate pattern that corresponds to the arcuate curvature of the wafer that the clamping component is adapted to engage. Thus, if the clamp member  236  is adapted to clamp onto the peripheral “free-zone” of a nominally twelve inch diameter wafer, the curvature of the edges  247  of the cross-bar would have a radius dimension of approximately 5.906″. Obviously, this radius dimension will vary depending on the size of the wafers to be gripped by the clamp member. 
     To provide a proper perspective of the size of the clamp member  236 , it is noted that the stem member  237  of a clamp member adapted to grip the peripheral “free-zone” of a nominally twelve inch diameter wafer is only 0.250″ wide. The overall length of the clamp member  236  amounts to only approximately 1.06″and possesses a thickness of only 0.30″ while the nominal width of the cross-bar  38  is approximately 0.180″. The through bores  242  and  243 , for instance, are only 0.032″ in diameter. Obviously, the dimensions noted are by way of example, and different dimensions could be used, particularly with different size wafers. 
     Referring to FIG. 23, it will be noted that the clamp members designated generally by the numeral  236  are associated with a diaphragm designated generally by the numeral  251  having an arcuate configuration as illustrated, to fit the conformation of a recess designated generally by the numeral  252  (FIG. 29) formed in the bottom plate  204  of the end-effector  201 . As illustrated in FIGS. 23 and 29, the diaphragm  251  is provided with a downwardly projecting peripheral rim  256  configured and having a depth sufficient to project into an arcuate groove  257  formed in the bottom plate  204 . the wafer clamp assemblies  226  in one embodiment include a monolithic mounting plate or piston  258  as illustrated in FIGS.  27  and  27 (A). This monolithic mounting plate or piston is essentially square, being only 0.6″ on each side and having a thickness of approximately 0.060″. Formed in the top surface of the piston  258  and extending transversely thereof from the left side to the right side as indicated in FIG. 27, is a groove  259  having a depth of approximately 0.050″, thus leaving a bottom wall portion  261  having a thickness of only approximately 0.010″. Formed in the bottom wall  261 , as illustrated in FIG. 27, is a generally rectangular aperture  262  adapted in one embodiment as illustrated in FIGS. 24 and 26 to receive the end projection  239  formed on the stem-portion  237  of the clamp member  236 . When properly positioned in the aperture  262 , the through-bore  242  in the projection  239  is in axial alignment with through-bores  263  and  264  formed in the piston  258  as illustrated. Thus positioned, the pin  266  illustrated in FIG. 29 is inserted through the bores  263  and  264  and through the bore  242  in the clamp member  236  to pivotally mount the clamp member  236  on the piston  258 . Additionally, the piston  258  is provided with threaded mounting bores  267  for a purpose which will hereinafter be explained. 
     As illustrated in FIG.  24  and FIGS. 30-31, where a vertical cross-section of the bottom plate  204  is illustrated, the diaphragm  251  is sealingly secured to the upper surface of the bottom plate  204  by placement of the superposed top plate which presses the peripheral flange  256  of the diaphragm into a receptive groove in the bottom plate. Each piston  258  for receiving each clamp arm or beam  236  is mounted centrally between the longitudinal edges of the diaphragm and are spaced apart as shown in FIG.  23 . To mount the piston  258  on the diaphragm, a spring plate designated generally by the numeral  271  and illustrated in FIGS.  28  and  28 (A) is attached to the underside of the diaphragm  251  as shown in FIG. 24, and attached thereto by machine screws  272  that pass upwardly through appropriate apertures  273  formed in the spring plate  271  as shown best in FIG.  28 (A). The spring plate  271  is provided with two downwardly projecting resiliently flexible tongue-like members or tangs  274  that are spaced apart from a third similar tang  276 . The tangs  274  are integral with the plate at their base ends and are displaced downwardly as seen in FIGS.  24  and  28 (A) so that the end portions  277  of the tangs  274  abut the bottom interior surface  278  of the bottom plate  204  as seen in FIG.  24 . In like manner, the tang  276  which lies between the tangs  274  but which extends in the opposite direction, has an end portion  279  which also abuts against the surface  278  of the bottom plate. 
     It will thus be seen that mounted as illustrated in FIG.  24  and FIGS. 30-33, the elastic resilience of the tangs  274  and  276  has the effect of biasing the diaphragm  251  upwardly below each piston  258 , causing the pin  266  to also be elevated, carrying with it the end portion  239  of the clamp stem  237 , thus causing the clamp member  236  to pivot clockwise about the pivot pin  279  (FIG. 24) so that the end portions  246  of each beam  236  normally move downwardly in the direction of the arrow, to close the gap  281  between the undersides of the members  246  and the top surface  282  of the bottom plate in the absence of a wafer  283  but which space  281  may be enlarged to permit entrance of the wafer “free-zone” peripheral portion when a vacuum is applied to the end-effector through the port  284 . 
     Thus, when the port  284  is connected to a source of vacuum, the reduced pressure within the recess below the diaphragm  251  causes the diaphragm to be drawn downwardly against the resilient tension in the tangs  274  and  276 , causing the piston  258  to move downwardly, carrying then pin  266  downwardly, and thus causing the clamp arm  236  to pivot counterclockwise, thus raising the grip end  246  of each clamp member  236  so as to open the gap  281  and permit the peripheral “free-zone” of the wafer to penetrate into the end-effector. It is for this reason that the embodiment of the invention illustrated in FIG. 24 is considered to a fail-safe embodiment. Since the vacuum system is used only momentarily to effect opening of the end-effector to admit the wafer, which vacuum is immediately discontinued once the wafer is properly positioned in the end-effector, the spring plate  271  automatically elevates the diaphragm and causes the clamp member  236  to clampdown tightly on the peripheral edge portion of the wafer. 
     It will be understood that under these conditions, the wafer will be held indefinitely gripped between the bottom surface of the clamp portion  246  and the top surface  282  of the bottom plate by the continued pressure exerted by the spring plate  271  against the underside of the diaphragm  251 . It requires activation of the vacuum system to break the grip of the end-effector on the wafer. For greater clarity, the structure illustrated in FIG. 24 is shown in exploded form in FIG.  30  and corresponding reference numbers have been applied to corresponding parts of the structure. 
     Referring to FIG. 31, it will be seen that this same embodiment of the invention, i.e., a normally-closed fail-safe end-effector that is opened by the application of vacuum pressure is illustrated with only slightly different components. In this embodiment illustrated in FIG. 31, the mode of operation is essentially the same as previously discussed, i.e., a normally-closed mode of operation that requires the application of negative or vacuum pressure to the interior of the end-effector shell to open the end-effector and release the wafer. Without the application of negative pressure, the end-effector remains tightly and reliably gripped to the peripheral “free-zone” of the wafer so that the wafer cannot be inadvertently released from the end-effector. In this view it will be seen that the top plate  203  is superimposed over the bottom plate  204  and secured by the screws  206  (FIGS. 17 and 18) to capture the diaphragm between the top plate  203  and the bottom plate  204  as previously described and illustrated. Superposition of the top plate Causes it to impinge on the peripheral margins of the diaphragm  251  to pressure seal it into the underlying groove formed in the top surface of the bottom plate and which defines the cavity  288  within which is captured the spring plate  271  previously described, dimensioned to impose a constant upward pressure on the underside of the diaphragm  251 , thus causing the pivoted end  289  of the clamp member  236  to be elevated, causing the clamp member  236  to pivot clockwise about then pin  291  as a fulcrum, and thus causing the lower edge  292  of the clamp member to be pressed tightly against the peripheral edge zone of the wafer  283  as previously explained. It will thus be seen that by connecting the passageway  293  which terminates at one end in the chamber  288 , to a source of vacuum, the diaphragm  251  will be drawn downwardly against the resilient pressure exerted by the spring  271 , causing the clamp arm  236  to pivot counterclockwise on the pin  291 , thus opening the end-effector by raising the surface  292  of the clamp member from the surface of the wafer, thus releasing the wafer. As previously discussed in regard to the structure depicted in FIG. 24, this structure oper4ates in a fail-safe mode in that once the gripping function has been performed on the wafer, it requires activation of the vacuum system to disengage the clamp member from the wafer, thus insuring that the wafer will not be inadvertently released from the end-effector. 
     The embodiment of the invention illustrated in FIG. 32, in contrast to the embodiment of the invention illustrated in FIGS. 24,  30  and  31 , operates by a standard mode of operation as distinguished from a fail-safe mode of operation. In this embodiment, the end-effector is again provided with a top plate  203  and a bottom plate  204  superimposed one above the other as illustrated and secured by screws as previously described but not shown in this view in the interest to clarity. They are retained in this position by appropriate screws  206  as illustrated in FIGS. 17 and 18. In this embodiment, the diaphragm  251  is again sealingly captured between the top and bottom plates. In this instance, however, the clamp member  236  is pivoted by the projection  241  (FIG. 26) and a pin  266 , while the left end of the clamp member  236  (FIG. 32) is pivoted by a pin  242  in the projection  239 . The diaphragm  251  seals the chamber  278  and a vacuum passageway  284  is provided for connection to an appropriate source of vacuum pressure. Disposed below the diaphragm  251  as previously described is a spring plate  271  that exerts an upward pressure on the diaphragm  251 , causing the midportion of the clamp arm  236  to be elevated, pivoting counterclockwise about the pin  242  at the left end of the clamp arm, and thus causing the clamping face  292  to normally be elevated and retained in an open condition by virtue of the pressure exerted by the spring plate  271 . Thus, in this mode of operation, the wafer  283  is inserted into the normally-open gap between the surface  292  of the clamp member and the bottom surface  282  of the bottom plate, and once properly inserted and positioned, suitable switches as previously described activate the vacuum system to draw or create a vacuum in the chamber  278 , causing the diaphragm to descend, pulling then pivot pin  266  downwardly, and causing the clamping ace  292  of the clamp member to impinge tightly against the “free-zone” surrounding the peripheral portion of the wafer  283 . Once the wafer has been properly inserted, positioned and clamped, the indicator  207  illustrated in FIG. 17 indicates the condition that exists, and in this case would indicate that clamping of the wafer has been completed. 
     Referring to FIG. 33, the embodiment of the invention illustrated operates in a normally open mode of operation and utilizes the components illustrated in FIGS. 29 and 30, with the exception that in this normally open embodiment of the invention, the clamp arm  236  is connected by the projection  241  and an appropriate pin  266  to the piston which in this embodiment is of the type of two-part piston that is illustrated in FIG.  29  and designated by the reference numeral  288 ′. 
     Thus, the piston parts are juxtaposed with a space between them to accept the width of the clamp arm  236  and a pin  266  extends through both of the piston parts  288 ′, and forms a pivotal journal for the clamp arm  236 . The left end of the clamp arm  236 , as shown in FIG. 33, is pivotally secured between the top and bottom plates by a pin  293  so that as the diaphragm  251  is elevated by the spring  271  (FIG.  28 (A), the clamp arm  236  is caused to pivot counterclockwise about the pin  293 , thus elevating the grip members  246  of the clamp arm, and opening the gap in the end-effector to receive appropriate insertion of the wafer  283 . 
     Once the wafer has been properly inserted, positioned and an indication given by the indicator  207  that it is properly loaded, a vacuum pump (not shown) is actuated to draw air from the chamber  288  through a passageway  284  as previously described, and the negative pressure within the chamber  288  causes the diaphragm  251  to be drawn downwardly against the pressure exerted against the diaphragm by the spring  271 . Such downward movement of the diaphragm causes the clamp member  236  to pivot clockwise, bringing the clamp members  246  downwardly into impinging contact with the peripheral “free-zone” of the wafer  283 . It will thus be seen that this structure operates in a normally-open, “standard” mode of operation in which retention of the wafer by the gripping members  246  is dependent upon the integrity of the vacuum system that retains the diaphragm  251  drawn downwardly against the pressure of the spring  271 . This the “standard” method that is utilized in the integrated circuit wafer industry to retain wafers “clamped” on the conventional vacuum operated surface of end-effectors that engage the bottom side or surface of the wafer. Accordingly, the end-effector of this embodiment is readily applicable to existing conventional equipment that is utilized in the vacuum-retention type of equipment. The advantage of this structure however is that no portion of the end-effector contacts the contamination-sensitive surfaces of the wafer, thus eliminating contamination which would otherwise be produced from handling and increasing the percentage of usable wafers that are produced without contamination. 
     Having thus described the invention, what is believed to be new and novel and sought to be protected by letters patent of the United States is as follows: