Abstract:
A system for handling stiff but flexible discs, particularly semiconductor wafers, including fail safe mechanisms that prevent the disc from being dropped if power to the unit is interrupted. Also, the electronics controlling operation resumes functioning at the point in the operation cycle existing when power was interrupted. A wafer hand assembly member is slipped under a wafer, or between parallel stacked but spaced wafers, and one or more fingers are rotated 90° to a position perpendicular to the plane of the stiff hand assembly member. The hand assembly also has one or more posts positioned perpendicular to the surface of the hand assembly. The finger(s) and post(s) or rear barrier constitute three upright projections or points forming the corners of a triangle with the wafer to be grasped there between. A translator solenoid or voice coil, controls the lateral location of one finger or post, moving that finger or post toward the other two stationary fingers or post(s) causing the wafer to be grasped with controlled traction force between the fixed posts and the moveable finger. The traction force is controlled by the amount of driving energy fed to the translator solenoid. If the power to the solenoid or voice is interrupted, springs in the system cause the disk to be held between the posts or barrier and fingers until power is restored.

Description:
This application is a Continuation-in-Part of U.S. application Ser. No. 09/245,010 filed Feb. 4, 1999, now U.S. Pat. No. 6,167,322 issued Dec. 26, 2000, which is a continuation-in-part of U.S. Ser. No. 09/113,857, filed Jul. 10, 1998, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Area of the Art 
     The present application relates to systems for the handling and local transport of disc shaped flat sheets of stiff but flexible materials such as integrated circuit wafers, flat screen displays, glass reticules used in semiconductor chip manufacture and the like materials. Particularly, the present invention relates to an intelligent integrated circuit wafer location and handling system and a method for selectively positioning and processing both sides of a subject wafer. 
     2. Description of the Prior Art 
     Semiconductor wafers are produced by complex multi-step processes. Sophisticated integrated circuit type electronic chips are derived from wafers during processes involving often greater than 100 steps. Many of steps require extremely accurate positioning of the chips because the submicron range technologies used in manufacturing the chips are both error and inspection intensive. Also, the wafers before processing are extremely expensive, and become even more valuable after processing. There is therefore a strong need for heightened control of processing and handling methods for the involved wafers. 
     It follows that the high production rates required for production of integrated circuits necessitate that the wafers upon which individual circuits are located be processed rapidly and in batches. Typical wafers being processed have diameters ranging from about 4 inches to about 12 inches. Such wafers are generally housed for processing in cassettes, or caddies in closely stacked vertical arrangements. 
     Processing generally entails separate removal of each subject wafer from its housing cassette and loading of the same into the processing equipment utilized, followed by return of the processed wafer to a cassette or carrier. The receiving cassette may be different than the first cassette, and the fragile nature of the wafers, generally silicon, provides further constraints. Removal, processing and repositioning of these varying sized wafers has created a longstanding need for more efficient apparatus and methods for processing them. Further, because the wafers are thin as well as formed from brittle materials, the pressure exerted on the wafers by the handling device can be critical and the gripping pressure must be carefully controlled to minimize bending, cracking or chipping of the costly wafers while still assuring a firm grip on the wafer to avoid dropping it during handling. 
     Patented Apr. 14, 1992, the WAFER INSPECTION SYSTEM of U.S. Pat. No. 5,105,147 (“Karasikov” et al.) is typical of the state of at least one aspect of the existing art. The disclosed system is for the semiautomatic inspection of printed circuits on silicon wafers. Included in the Karasikov patent are the combination of a floating table, and a robotic arm optical inspection device which includes a sophisticated optoscanner for the alignment and positioning of a wafer. 
     Karasikov removes involved wafers by applying a vacuum to a narrow zone at the circumference of a wafer. The mechanism of the Karasikov patent highlights problems, which result in many of the processing errors ameliorated by the teachings of the present invention. 
     Likewise, U.S. Pat. No. 5,504,345 (“Bartunek” et al.) which issued Apr. 2, 1996, disclosed a dual beam sensor and edge detection system and method. Two light sources, or solid state lasers, are used to detect the edges of the involved wafers. The Bartunek patent essentially shows that lasers may be used for the detection of, for example, the reflective surface of a wafer or optical disc. 
     Other known systems for wafer handling similarly either address improvements in locating wafers or quasi-automated means for handling wafers. It would be highly advantageous to have the capability for concurrently improving the performance of both of these functions within a single system. Capitalizing upon the use of lasers without the drawbacks of vacuum-based technology would solve many longstanding needs. 
     By way of example, current technology often uses a vacuum chuck mounted on a robotic arm to remove or replace individual wafers in the cassettes. Since the position of each cassette and each wafer within the cassettes is unique, the location of each disk within the three ordinal planes (“X, Y, and Z”) relative to some reference has to be entered into the software driving system controlling the robotics that handle the wafers. 
     Existing methodology requires mechanical measurement of each location followed by the data being manually entered into the software being utilized. This is a time consuming process additionally constrained by the high likelihood of human error. Sufficient differences exist among known cassettes and cassette holders, that a calibration of every cassette to be employed is generally required. 
     Further, these constraints are complicated by the fact that, for example, in semi-portable processing systems, relocation of any part of the system requires new calibration. 
     Conventional vacuum chucks, or pickup devices, referred to as vacuum end effectors, further induce harmful artifacts of the processing steps and these artifacts can result in lower industrial efficacy. Any warpage in the employed vacuum pickups may cause malfunctioring because of air leaks. Since the vacuum pickups must be thin and contain air passages, they are difficult and expensive to build. Further, since the wafer is held by the surface, the wafer is prone to slip under the high acceleration rates necessary in high speed processing. Any misalignment of the disk with the end effector can cause the system to crash. Contamination of the surface by the vacuum pickup parts on the end effector itself occurs with alarming frequency. 
     Likewise, a clear need exists for a way to process both sides of a semiconductor wafer. Among the prior art, various attempts at solutions to related problems, and methods for handling wafers for processing are illustrative of the paucity of patents actually addressing the above enumerated constraints. The state of the art clearly shows a need for improvement, such as taught by the present invention. 
     Another method of lifting wafers is the use of mechanical grippers, U.S. Pat. No. 5,570,920 (“Crisman” et al.) issued Nov. 5, 1996, utilizes a DC motor to drive a robotic finger. Unlike the teachings of the present invention, strain gauges 171, 173, 175 on the inner surfaces of the fingers are used to sense gripping pressure and, once an over pressure is sensed, stop the motor. 
     By way of further example, U.S. Pat. No. 5,435,133, which issued Jun. 13, 1995 (“Yasuhara” et al.) utilizes servo motors which drive robotic fingers based on positioning signals. However, no sensors to indicate or control grasping force were found. Likewise, the complex attaching/detaching portion of the hand portion was the focus of Yasuhara&#39;s disclosure, differentiating this patent from the teachings of the present invention. 
     Additionally, U.S. Pat. No. 5,378,033 (“Guo” et al.), which issued Jan. 3, 1995, utilizes a single drive mechanism for all of the involved mechanical fingers so that they apply a uniform force on the object grasped. The Guo patent teaches a purely mechanical robotic or prosthetic hand. However, the method of controlling the drive mechanism was not apparent, differentiating the Guo patent from the teachings of the present invention. 
     U.S. Pat. No. 5,280,981 (“Schulz”) issued Jan. 25, 1994 uses a load responsive two-speed drive assembly and a slip clutch (Col 9, line 63-col 10, line 28). Notably, the digit actuation mechanism of the Schulz patent contemplates neither using solenoids, voice coils nor other current generation means wherein a force directly proportional to current is used. 
     U.S. Pat. No. 5,188,501 (“Tomita” et al.) issued Feb. 23, 1992, was directed to a wafer transfer system which uses a set of claws which pivot under a wafer to serve as a lifting platform for the wafer. The Tomita patent is thus different from the teachings of the present invention because it works by creating a lifting force which cradles the wafer rather than applying a grasping force. 
     Issued Dec. 22, 1992, the “Jacobsen” U.S. Pat. No. 5,172,951 does not appear to disclose a tension sensing or controlling technique. This ROBOTIC GRASPING APPARATUS operates with three degree of freedom, yet does not disclose wafer-friendly usages such as those which are an object of the present invention. 
     U.S. Pat. No. 5,108,140 (“Bartholet”) issued Apr. 4, 1992, includes a palm plate and grippers having tactile or other sensors on its upper surface to detect the position of the payload or to provide input to the control mechanism (Col 5. lines 20-37). 
     A parallel vise like grip is generated but no means of detecting or controlling the gripping force appears to be given. 
     Likewise, the “Ulrich” U.S. Pat. No. 5,501,49 (issued Mar. 26, 1996) and U.S. Pat. No. 4,957,320 (issued Sep. 18 1990) each use tactile sensors 200, 210 located on the palmar surfaces of the fingers and the palm. 
     U.S. Pat. No. 4,354,553 (“Rovetta” et al.) issued Sep. 28, 1982 shows a three finger grasping system where the force applied by the fingers is supplied by traction cables 42, 43, 44 along the inner surface of the fingers such that tension applied to the fingers causes the fingers to pivot inward, tightening the grasp on the held object. Sensors 84, 85, 86, shown in FIG. 6 of the Rovetta patent, attached to the tension cables sense the traction force applied thereto, differentiating the Rovetta patent from the teachings of the present invention. 
     U.S. Pat. No. 4,654,793 (“Guinot”) also incorporates strain gauges 26, 28 on the fingers. 
     U.S. Pat. No. 6,092,971 to Balg et al is direceted to a system for removing wafers from a carrier using a robotic arm. This system uses a combination of a holding rake, several gripping heads which swivel and a counter holder, all of which must be used to grasp and remove the wafers. 
     Accordingly, since nothing among the prior art has adequately addressed the longstanding needs ameliorated by the present invention, an intelligent integrated circuit wafer handling system is offered to meet these needs. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a system which overcomes the drawbacks of the prior art for chip holding apparatus and techniques. It is a farther objective to prove fail-safe means should power feed to the holding device be interrupted. It is a still further objective to provide fail safe means, which do not adversely effect the grasping sensitivity of the grasping fingers and posts during normal operation. 
     Briefly stated, there is provided a system for handling stiff but flexible discs, particularly semiconductor wafers, which is capable of allowing processing on both sides of a wafer. Optical beams can be employed to detect a wafer&#39;s edge and ascertain a wafer position. Grasping by a unique robotic wafer hand assembly  101  plugged into other robotic systems for positioning is taught. A stiff wafer hand assembly member has one or more actuating rods disposed either centrally or spaced apart along the length of the member. As the wafer hand assembly member is slipped under a wafer, or between parallel stacked, spaced wafers, one or more rotating fingers, which begin in a released position are rotated 90 degrees and spaced from the wafer edge. A translator solenoid, voice coil, or combination thereof acting through an arm, applies lateral movement to the finger or a separate post to grasp the wafer. A rotator solenoid or coil  109  turns the finger 90°. This combination presents a thin profile so the wafer hand assembly member can be inserted under a top wafer between stacked, spaced wafers in a tray as shown in FIG. 8, or rotated 180° to pick up the wafer residing in a processing device. Once positioned under, over or along side a wafer, the finger is rotated to the vertical position by the rotator solenoid. Depending on the embodiment, the finger is pulled or the post is pushed in by the translator solenoid, grasping the wafer with controlled traction force between the post(s) and the movable finger(s). Methods for use of the apparatus of the system of the present invention are also taught. 
     A further improvement is the addition of fail safe systems. The disks handled by the disk handling systems are fragile and if dropped can readily chip or crack. In prior available vacuum, pneumatic and electrical systems, a major drawback has been a loss or reduction of the gripping action if power to the gripper control is interrupted due to a power failure or fluctuations in the electrical control circuit. This deficiency has been eliminated in the presently described devices by adding a closing spring specifically selected to have a force, either in expansion or compression, to positively grip the disk held by the handling system if the electricity, or other force supplying means, inadvertently decreases below the force necessary to adequately hold the disc. At the same time, the spring is selected so that, should there be a total failure of the force holding the disks, the force now applied solely by the spring is such that the disks will not be damaged by the gripping means. Also included are sensing means to indicate the position of the finger and whether a disk is held in the gripper. As shown schematically in FIG. 8, the wafers are usually carried in a tray. In various different embodiments of the tray  150 , the circular wafer may contact and rest on the tray sides and/or the tray bottom. More specifically, the lower most point of the wafer as it rests in the tray  150  may be in contact with a point in the center of the tray bottom (See FIG.  9 ). 
     In an alternative tray design the wafer may only contact the sides of the tray thus spacing the bottom of the wafer from the tray bottom. As a further alternative, the tray bottom may have an opening along the length thereof. If the wafer is sufficiently spaced from the bottom of the tray  150 , or there is an open space in the tray bottom the wafer handling system of FIGS. 1-8, having a centrally located rotatable finger, can be used. However, if the wafer contacts the bottom of the tray  150  along the tray center line then the rotatable fingers must be spaced from the center of the front edge  124  of the handling system as shown in the embodiment of FIGS. 9-11 and more particularly in FIG.  9 . 
     According to a feature of the present invention, there is provided a system for handling wafers and the like substrate means, which comprises, in combination, a hand assembly, a means for grasping, transporting and returning said substrate means to be handled, and at least a control means for programming and implementing a desired sequence of operations. This system may also include a separate or integral optical means for detecting a local position and orientation of a substrate means to be handled. 
     The system may further include optical detection means in combination with computer based identification calibration and control means for determining the size or identity of the wafers and subsequent control of the movement and positioning of the moving finger and the tension placed on the wafer grasped by the system. 
     According to another feature of the present invention there is provided a method for handling wafers, and related compact planar devices without damaging their surface integrity, the method comprising the steps of: 
     a) providing a robotic wafer hand assembly equipped with at least one or more posts, which may be fixed or moveable, a rotating finger and optical sensing means, which robotic wafer hand assembly is attached to other robotic systems for positioning; 
     b) reading a plurality of data regarding the relative position and orientation of a plurality of wafers; 
     c) grasping a wafer by use of an actuating rod disposed in a central portion of said robotic wafer; 
     d) locking the wafer between the post(s) and the figure(s); 
     e) transporting the wafer to a desired location, processing the wafer; 
     f) releasing said wafer into a desired location, and 
     g) repeating each of said steps for a subsequent wafer. 
     According to a feature of the present invention, there is provided a system for handling wafers and the like substrate means, which comprises, in combination, a hand assembly, an optical means for detecting a local position and orientation of a substrate means to be handled, a means for grasping, transporting and returning said substrate means to be handled, and at least a control means for programming and implementing a desired sequence of operations. 
     The system may further include optical detection means in combination with computer based identification calibration and control means for determining the size or identity of the wafers and subsequent control of the movement and positioning of the moving finger and the tension placed on the wafer grasped by the system. 
     According to another feature of the present invention there is provided a method for handling wafers, and related compact planar devices without damaging their surface integrity, the method comprising the steps of, providing a robotic wafer hand assembly equipped with at least two fixed posts, a rotating finger and optical sensing means, which robotic wafer hand assembly is attached to other robotic systems for positioning, reading a plurality of data regarding the relative position and orientation of a plurality of wafers, grasping a wafer by use of an actuating rod disposed in a central portion of said robotic wafer, locking the wafer between the fixed posts and the finger, transporting the wafer to a desired location, processing the wafer; releasing said wafer into a desired location, and repeating each of said steps for a subsequent wafer. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     The above-mentioned and other features of this invention and the manner of obtaining them will become more apparent, and will be best understood by reference to the following description, taken in conjunction with the accompanying drawings. These drawings depict only a typical embodiment of the invention and do not therefore limit its scope. They serve to add specificity and detail, in which: 
     FIG. 1 is a perspective top plan view of a first version of a robotics wafer hand assembly according to an embodiment of the present invention; 
     FIG. 2 a, b , and  c  are detailed views of enlarged portions of FIG. 1, showing the rotating finger in three different positions; 
     FIG. 3 is an enlarged detailed view of FIG. 1 showing one of the fixed pressure posts; 
     FIG. 4 is an additional perspective bottom plan view of a robotics wafer hand assembly according to an embodiment of the present invention as depicted in FIG. 1, showing a finger actuating rod, a finger translator solenoid and a finger rotating solenoid; 
     FIG. 5 is a side view of a modified version of the robotics wafer hand assembly according to an embodiment of the present invention with certain of the components relocated to the top of the assembly; 
     FIG. 6 is a top plan view of the embodiment of FIG. 5 showing a robotics wafer hand assembly according to an embodiment of the present invention with a wafer disposed thereupon the structure underlying the wafer also being shown; 
     FIG. 7 is a schematic perspective top plan view of a robotics wafer hand assembly according to an embodiment of the present invention showing the cooperative interplay of each of the described and claimed elements above and below the paddle as if the paddle were transparent; 
     FIG. 8 is a schematic perspective top plan view of a series of wafers in a carrier. 
     FIG. 9 is a top view of a further embodiment with two rotating fingers and a single moveable post. 
     FIG. 10 is a side view of the embodiment of FIG.  9 . 
     FIG. 11 is a top view of a modification of the embodiment of FIG. 9 with flexible, rotational actuating rods. 
     FIG. 12 is a top schematic cutaway view of a coil assembly with a fail safe spring mechanism. 
     FIG. 13 is an end schematic cutaway view of the coil assembly with the fail safe spring mechanism of FIG.  12 . 
     FIG. 14 is a top schematic cutaway view of a solenoid assembly with a fail safe spring mechanism. 
     FIG. 15 is an end schematic cutaway view of the solenoid assembly with the fail safe spring mechanism of FIG.  14 . 
     FIG. 16 is a top schematic cutaway view of the coil assembly with a fail safe spring mechanism of FIG. 12 installed in the wafer hand of FIGS. 1-7, which includes a single rotating finger. 
    
    
     The invention is defined in its fullest scope in the appended claims and is described below in its preferred embodiments. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Disclosed is a system to handle flat stiff but flexible discs, such as semiconductor wafers, that is capable of allowing processing on both sides of any respective wafer. The system may employ optical beams or other sensor techniques to detect the wafer edge and consequently the wafer position. The system also incorporates unique grasping pressure control means. A unique robotics hand then grasps the wafer in such a manner as to allow rotation through 360 degrees around the long axis of the hand or angular movement up or down much the same as flexing the natural wrist, or rotating the hand or arm. The hand design is such that it plugs into or otherwise attaches to positioning robotics. This permits quick interchange of configurations (size for example) and minimum downtime for maintenance. 
     The system likewise employs state-of-the-art robotics to control all positioning functions. This includes computer technology as well as specialized electronics. Software driving the system is necessarily unique to the required application, but is structured as compatible with existing commercially available software. Data output may include any or all of the common technologies now in use, or those within the technical knowledge of an artisan. 
     As discussed in detail below, at least six major subsystems are found within or used in conjunction with preferred embodiments of the present invention: 
     1) a robotics ‘hand’ to grasp the wafers and allow them to be rotated through 360 degrees for processing on both sides; 2) an optical reading or other sensor system that accurately locates the position of each wafer, enabling the ‘hand’ to access the wafer without breakage; 3) a data processing and control system to control the hand and associated mechanics and to act on the data supplied by the optical subsystem; 4) control means to select the appropriate pressure or tension applied to the wafer; 5) both software and firmware to drive the system, and 6) a mechanical fail safe system to prevent water loss during a power failure. 
     In addition to being used for wafer processing, the system of the present invention can be used in other applications. This would include, but not be limited to, magnetic disk processing, CD ROM processing, processing of flat screen displays, handling of reticules in semiconductor chip processing, gene chip handling, and in general any process that could utilize a robotics hand with these characteristics. The ability to uniquely locate a part makes the proposed system an exceptional and unique candidate for inventory, parts tracking, and all other manufacturing processes where it is required, or beneficial, to keep track of the number and location of assemblies. 
     A particular example of uses of a preferred embodiment of the present invention is for placing wafers into specific cassettes or caddies for different processing steps. This exemplary embodiment is offered hereafter as demonstrative of examples of the working models of the present invention and is not meant to be limiting of the claimed subject matter of the present invention, Accordingly, while the embodiment is representative of the subject matter set forth in the claims appended hereto, it is in no way meant to limit the same. 
     Referring now to FIG. 1, a robotics wafer hand assembly  101  includes a paddle  100 , which is made up of 2 thin stiff members secured together, for ease of manufacturing, to form a single thin stiff member, made from a material appropriate for the application, with two fixed pressure posts  103  located thereon, and a rotating finger  105  at the end thereof located in opposition to the posts  103 . Mounted to the wafer hand assembly  101  are the actuating mechanisms to rotate the finger  105  and locating/positioning optics mount  107 . The stiff members may be secured by typical assembly means such as screws, adhesives, rivets or other comparable means. 
     Design of the wafer hand assembly  101  is such that it can plug into or be otherwise attached to a robotics arm (not shown) at a first end proximate to optics mount  107  using hand mount  115 , or other suitable mounting or connecting means common in the industry. Also included would be electrical and data coupling means to attach the hand to control systems. This permits quick removal for repair. Also, various configurations of the wafer hand assembly  101 ; e.g. different sizes, can be interchanged in minimal time. Such combination with known systems and interchanging would be known to those working with such systems; therefore, further detail regarding the same has been omitted. 
     Once the desired optical readings are taken and the programmed sequence of operations to be performed ascertained, lifting hand  101  grabs a wafer at three points of the disk. Two of the points  103  are in fixed locations spaced apart on a circumferential line with the radius equal to approximately that of the wafer. At each point is a small post  103  with small groove  126  to hold the edge of the wafer. The third lifting point is the moveable finger  105  that supplies the clinching action for the lift. 
     Wafer hand assembly  101  moves to the wafer with the finger  105  retracted. In the retracted position, the finger  105  rotates 90 degrees, so it now has the same orientation as the other posts, and is drawn back toward the other two holding points  103 . This action holds the wafer between the posts  103  and the finger  105 . 
     Rotation of the finger can be accomplished electromechanically or merely mechanically by a cam. Cam operation simplifies the electronics, but is subject to wear, lubrication, and contamination factors. In addition, more machining may be required. It is also contemplated that the finger  105  in its retracted position may point along the axis, and in the plane of the hand  101 , rather than perpendicular to the axis as shown on FIG. 2 a.    
     Referring now to FIGS. 2 a, b , and  c  and FIG. 3, detailed views of a rotating finger  105  and of one of two fixed pressure posts  103  according to the embodiment of the present invention are shown. Wafer hand assembly  101  member has an actuating rod  111  disposed in a central portion thereof (see FIG.  7 ). When the assembly  101  is formed of two sheets of material, the actuating rod may be disposed in a channel between the two sheets of material so that it is not externally exposed. The wafer hand assembly  101  as shown in FIG. 2 a , is slipped under a wafer  122 , or between two wafers in a stack (FIG. 8) and rotating finger  105 , is rotated 90  to the position shown in FIG. 2 b . At this point, the finger  105  is spaced from the wafer hand assembly  101  front edge  124 . It is then moved toward the wafer hand assembly edge  124  as shown in FIG. 2 c  to grasp the wafer  122  between finger  105  and posts  103  as shown in FIG.  6 . 
     Referring to FIGS.  1  and  4 - 7 , a translator solenoid or voice coil  117 , through an arm  119 , positions the finger  105  outwardly while a rotator device  109 , such as a solenoid, motor or similar translational and/or rotational device turns the finger  105  90°, presenting a lower profile whereby the wafer hand assembly  101  member can be inserted between wafers or rotated 180 degrees to pick up the wafer from the top. Once positioned under, over or between wafers  122 , the finger  105  is rotated to the vertical position by the rotator solenoid  109  (see FIG. 2 b ) and then is pulled in by the translator solenoid  117  (see FIG. 2 c ). 
     Finger translator solenoid  117  or similar electrically powered translational device, finger rotator device  109 , and finger actuating rod  111 , as discussed in detail below, cooperatively act for effective grasping and releasing of a wafer (or the like substrate member item to be held), and holding the same in a fixed position for transfer from one processing location to another, without breaking or dropping the wafer or bending it beyond acceptable limits Likewise, a substrate member may be released and picked up at a position 180 degrees from its released position. 
     Finger actuating rod  111  is driven by the magnetic coil energized and controlled by finger translator solenoid  117  and finger rotator solenoid  109 , as discussed in further detail below. 
     The wafer hand assembly  101  member has an actuating rod  111  disposed in a central portion thereof. 
     Translator solenoid  117 , through an arm  119  attached thereto, pushes the finger  105  in or out while rotator solenoid  109  turns finger  105  90°, presenting a lower profile whereby the wafer hand assembly  101  member can be inserted between wafer  122  or manipulated 180° to pick up the wafer  122  from the top or bottom. Once positioned under, over or alongside a wafer  122 , the finger  105  is rotated to the vertical position (FIG. 2 b ) by the rotator solenoid  109  and then is pulled in (FIG. 2 c ) by the translator solenoid  117 , locking the wafer  122  between the fixed posts  103  and the finger  105 , as shown in FIG.  6 . 
     Grasping action is accomplished by using finger  105  to pressure a wafer against fixed posts  103 . This is very much like the natural grasping action of the human hand with the opposable thumb applying pressure on an object held against the fingers. Likewise, as mentioned above and treated in detail below, the analogy between wafer hand assembly  101  and the human arm includes the 180 degree rotation which would be characterized by, or controlled, like the action of a human wrist in changing the position of a human arm from one with a top side facing up to a top side facing down. 
     In the release mode, the finger  105  lies in the plane of the hand  101 . Positioning of the finger  105  is accomplished through the controlling mechanics at the ‘wrist’ (or proximate) end of hand  101 . In particular, a voice coil or motor/encoder combination is used to position finger  105 . 
     Hand  101 , while in the release mode, is positioned under the wafer selected using electronics positioning systems or an optics system shown schematically at  117 . At this point, the finger  105  is rotated so as to present a surface to the wafer edge. The controlling mechanics then pulls the finger  105  towards the center of the wafer thereby pushing the wafer against the fixed diametrically opposed posts  103 . Pressure is accurately maintained through precise control of the electrical current applied to the coil driving translator solenoid or voice coil  117 , which, in turn, causes the actuating rod  111  to move along the length of the hand  101 . Leads  123  to the controls communicate information from a central processor (not shown) to the hand  101 . It has been found that supplying a current of about 310 mA to about 360 mA to a solenoid supplied (Model B LA13-12-00A) exerts the appropriate grasping pressure on a 200 nmg (approx. 12″) wafer held in the device. 
     Typically, finger movement as effected by finger translator means  117  and finger rotator device  109  is programmed on an application specific basis. Likewise, the same can be accomplished by accurately controlling the current through voice coils and employing stops and cams where necessary. However, any of the mechanisms used in the field of motion control could be used when applicable. Once the wafer is grasped, the hand  101  can now transport the wafer to any location directed by the robotics. The exemplary feature of this grasping method is that it allows the hand to completely rotate the wafer through 360 degrees without dropping it, permitting the wafer to be placed in a variety of carrier mechanisms. The ability to rotate as such will allow processing of both sides of the wafer. In addition, since the wafer is trapped between the posts  103  and finger  105 , it can be moved at greater accelerations and speeds than possible with vacuum pickups, thereby reducing processing time. As an added benefit, the wafer surface is not contaminated since only the edges come in contact with the hand. This will enhance production yields. 
     Referring to FIGS. 9 and 10, a further embodiment of the wafer handling assembly  201  includes a stiff member or paddle  200  with a single moveable post  203  centrally located at the control end  204  of the paddle  200  and two rotatable fingers  205  at the opposite end of the paddle, to form the three corners of a triangle for grasping a wafer  222  there between. Mounted to the wafer handling assembly  201  are two rotation coils  209 , each connected to a finger  205 , and a translational coil  217  for moving the post  203  a sufficient distance along the central axis  206  of the assembly  201  to grasp a wafer  222  with the desired tension between the post  203  and the fingers  205 . As in the previously described embodiments the assembly  201  may also carry locating and positioning optics and related controls. 
     In contrast to the previous embodiment, in the embodiment of FIGS. 9 and 10 the two spaced apart fingers  205  rotate from the plane of the paddle  200  as a result of a rotational force applied to actuating rod  211  to a position perpendicular to the paddle surface. However, they do not translate lengthwise. Instead, the single post  203  is moved along the central axis  206  of the paddle  200  to grasp the wafer, the tension on the wafer  222  being controlled by the current applied to the translational coil or solenoid  217 , operating through the translational rod  218 , which moves the post  203  to apply grasping pressure to the wafer  222 . Otherwise, this embodiment operates in a similar manner to the previous described embodiment. The paddle  200  is positioned next to a wafer  222 . The rotational solenoids  209 , operating through actuating rod  211 , causes the finger  205  to move into its perpendicular position with the wafer against the fingers  205 . 
     One skilled in the art based on the foregoing description will recognize that all of the supplemental features of the first described embodiment, including the optical sensing and positioning devices can be used on the further embodiment described above. 
     FIG. 11 is a wafer handling system  301  which is a modification of the embodiment of FIGS. 9 and 10 having the rotation of the fingers caused by a rotational force applied to a flexible actuating rod  311 . As shown in FIG. 11, rather than the rod  311  being straight is flexible and therefore capable of maintaining the same alignment from rotational solenoid  209  (not shown in FIG. 11) to the finger  205 . Otherwise, the modification of FIG. 11 operates in the same manner as the embodiment of FIG.  9 . 
     FIGS. 12-16 show two embodiments of the drive components assembly  300 ,  400  for the rotatable finger and translational finger or post which incorporate a biasing spring. When power is not delivered to the coil  301  or solenoid  401  which controls the translational movement of the finger  105  or post  103  the spring  311  provides a biasing movement to that finger or post. The tension of that spring, whether it is operating to expand or contract, is selected so that the tension applied to the disk  122  being grasped does not exceed a predetermined maximum level needed to grasp the disk  122  without damaging it and is not less than a tension level necessary to hold the disk. Because the assembly can be constructed so that the translational post or finger is at its further-most position (i.e., always open) when powered but at rest (not grasping a disk), or at its nearest most position (i.e., always closed) in the same rest mode the spring can be alternatively placed in the drive components assembly in tension or compression. 
     FIGS. 12 and 13 show a top and end view of the drive components assembly  300  incorporating a voice coil  301  to provide movement to the translational post or finger  105 . FIGS. 14 and 15 show the drive components assembly  400  with the voice coil  301  replaced by a solenoid  401 . The main difference between the voice coil and the solenoid is that in use of the voice coil, the tension on the disk applied by the translational post or finger is proportional, over the operating range of the coil, to the current applied to the coil. While some tension differential can be provided by adjusting the current to the solenoid, it generally operates in an on/off condition with the tension applied to the disk being dictated by the particular solenoid chosen and its operating characteristic at the prescribed current feed. 
     An additional feature of the embodiments in FIGS. 12-15 are that they are all provided in an insertable frame or assembly base  308  so the drive components assembly can be reassembled and then inserted into any of several different configurations of the wafer grasping hands. It can be seen, by comparing the embodiments of FIGS. 12-15 with the embodiments of the other Figures, that in the prior embodiments the translational and rotational drive components were mounted directly to the hand assembly, and had to be individually assembled to the unit, rather than being attached to the hand assembly as a single unit. Incorporation of the embodiments of FIGS. 12-14 requires only that the drive components assembly  300 ,  400  be mounted to the hand assembly and the actuating rod  111  be attached to the finger shaft coupling  305  in the drive components assembly. It should be noted that while FIGS. 12-15 show only a single finger which both rotates and translates, the drive components assembly can be configured to include drives for attachment to additional fingers or to separate rotational fingers and translational posts. 
     Another problem with prior available devices is that it is difficult for the operator, or electronics controlling the operation of the disk handling assembly, to determine during operation if the finger was in an up or down position, was in its extended (open) position or withdrawn (grasping) position or whether a disk was being held or the hand failed to grasp a disk. The latter problem may be caused by several operational deficiencies, such as a disk not being in the pickup location when the hand attempted to grasp it, a disk was dropped or not properly grasped for several different reasons, the disk which was attempted to be picked up was defective (broken, chipped etc.) or the shaft attached to the finger was damaged or disconnected from the drive mechanism. These problems are addressed by the embodiments of FIGS. 12-15 which include a first sensor means to determine if the finger is up or down and a second sensor means for finger in-or-out position. The finger in-or-out sensor may also sense if a disk is being grasped by indicating that the finger has moved translationally inward further than if a disk were present. This, in turn, can provide warning lights, alarms, or shut down the system for inspection and or repair. One skilled in the art can readily identify suitable optical, mechanical or electronic sensors typically used to sense positions or presence of mechanical components. 
     The drive component assembly  300  of FIGS. 12,  13  and  15  comprises 
     a) a voice coil assembly  301  which acts to move the grasping finger  105  longitudinally along the hand  101  to grasp the disk  122  between the translational finger  105  and a raised, grooved barrier  315  which serves the same function as the fixed posts  103 , 
     b) a motor  304  which provides rotational motion to the finger  105  by turning the actuating rod  111 , and 
     c) a tensioning spring  311  which acts to apply a fixed tension on the finger when it grasps a disk  122 . 
     The voice coil is comprised of a pillow block magnet assembly  309  and a pillow block coil assembly  310 . Providing a measured amount of electrical current to the coil assembly  310  causes the magnet assembly to move a fixed predetermined distance, in relationship to the coil, with a predetermined force, causing the bridge  302 , to which either the coil or magnet is attached, to move longitudinally the same fixed distance. This in turn moves the actuating rod  111  and the finger  105  attached thereto, the same distance. Other components are: 
     a) a coupler  305  for attaching the rod  105  to the rotational motor  304   
     b) a spring adjustment stop  306  which is moved along the spring shaft  307  to adjust the tension applied by the spring to the finger through the drive component assembly  300 , 
     c) a fixed rotation stop  312  which can be set to limit the rotation of the finger from horozontal to vertical (i.e., 90°) 
     d) a rotation sensor  313  to detect if the finger is up or down, and 
     e) and an in-or-out sensor  314  to detect if the finger is in its extended or retracted position. 
     These components are fixedly or moveably mounted, as required by their operation, to an assembly base  308  which is, in turn mounted to the hand assembly  101  as shown in FIG.  15 . The spring  311  may be replaced by other similarly acting devices such a magnetic break. 
     The drive component assembly  400  of FIGS. 14 and 15 is assembled and operates substantial the same as the assembly of FIGS. 12 and 13 with the exception that the voice coil  301  is replaced by a solenoid  401  mounted to the assembly base  308 . The movement of the solenoid plunger  402  provides longitudinal movement of the finger  105  which was provided by the magnet assembly  309  of the voice coil. 
     Wafers are normally loaded in cassettes or caddies and are stacked in grooves that hold the wafer on the sides. The present system will locate the position of each wafer to a high degree of accuracy by employing light beams and photo sensors to detect the wafer edge. Changes in the reflections from the edge allows the optical sensing equipment to determine the wafer edge and, therefore, the position of the hand with respect to the wafer. The entire caddie can be scanned and all positions determined, including missing wafers, as a missing wafer will generate an anomaly in the spacing sequence. 
     Sensing optics mount  107  is centrally mounted on the ‘wrist’ end of hand  101  as shown in FIGS. 1 and 4 or off to one side as shown in FIG.  6 . The optics system in preferred embodiments is comprised of optical transmitters such as lasers and IR diodes, optical receivers such as photo diodes, CCD&#39;S, photo transistors, and similar devices and the associated mechanical devices needed to direct an illuminating beam(s) at the edge of the wafer and receive the reflections. The beam(s) are focused at an optimal distance from the finger end of the hand that will permit accurate and reliable position determination. The beam(s) can be modulated in intensity and position to reduce the effects of background noise and to enhance edge detection. More than one sensing optics mount  107  can be used, such as a second unit (not shown) at a similar location on the other edge of the face of the assembly to aid in positioning. Also, additional optical sensors  130  can be located on the hand  101  at various locations to aid in accurately measuring the size of wafer  122 . 
     Panning the small focal point across the face of the edge will allow an accurate location of the edge vertices and consequently the wafer itself Since the edge of the wafer represents a compound surface, reflections from the surface may or may not reach the receivers. Panning the beam(s) along the edge will increase the probability of detection and increase accuracy since the wafer radial line aligned along the long axis of the hand will produce the greatest reflection. This information will allow the robotics to generate the best hand alignment with reference to the wafer. 
     This system is driven by robotics of the form necessary to the application or process. Any of the digital/analog techniques used for determining position, speed, acceleration, and, in general, all parameters associated with displacement and motion may be used as applicable to the specific process. The system of the present invention further embodies the use of computer equipment in conjunction with process specific electromechanical, pneumatic, and hydraulic systems to attain the desired operation. 
     The control system which is contemplated as within the scope of the instant teachings likewise serves to direct and modulate the photo sources, position the photo detectors, analyze the data from the detectors representing the variations in reflections, use the processed data to direct the motion control units to position the equipment as desired, and to process the feedback data from the motion control units to determine correction signals. 
     Further mechanisms used in conjunction with this system generate any alarms, signals and/or bells required, and format and output required data as video, print, audio, telephony, telemetry or as any of the other communications technologies necessary. 
     Since the system of the present invention has a wide range of applications, material used in the fabrication of this system will necessarily be diverse. This is to include, but not be limited to, metals, plastics, ceramics, glass, wood and all the various alloys, grades, tempers, compounds, and varieties of such, including compounds and combinations. The specific application and environment will dictate the actual materials used. 
     As discussed, related improvements according to the teachings of the present invention include replacement of conventional teachings with dynamic automated system employing laser-measuring equipment. Likewise, it is contemplated by the present invention to replace existing vacuum pickup technology with an electromechanical or gas actuated system that does not rely on a vacuum and provides a positive lift and retention system. 
     Modern laser distance measuring equipment is capable of making very precise measurements. Suitably locating one or more laser reading heads will provide all the information necessary to accurately locate and size each wafer in the processing system. Typically, a laser head located as reference on a two-axis mount would sweep the column of wafers in a cassette. 
     The shown locations are not intended to limit the location or number of optical sensors. The reflection from the individual disks provide the line-of-sight distance from the reference. Further, a reading from the second optical sensor  130  located on the center line of the hand  101 , when taken in conjunction with the known position of the posts  103 , can be used to sense the exact location of the edge of a circular wafer disc and in turn determine the exact diameter of the disc for use in setting the current delivered to the tensioning device. 
     Encoders in the axis mounts likewise are effective for supplying azimuth information, as is known to artisans. From the combined information, sent to a central processor, the exact position of each wafer relative to the reference can be determined to a high degree of precision. This same process is applied to the destination locations of each wafer. The processor then utilizes the information to exactly place the wafers, as needed in cassettes or caddies. 
     Different metals and plastics are used according to the teachings of the present invention. The environment where the unit is used will determine the materials of construction. Mechanical interface to the different types of robots requires many different mechanical designs. However, this does not effect the smooth operation of the intelligent integrated wafer handling system. For example, all the different mechanical designs can utilize the modular assemblies of FIGS. 12-15. 
     To avoid bending or cracking of a wafer being grasped, the amount of pressure applied by the moveable finger  105  must be controlled precisely. The embodiment of the present invention described above utilizes an actuator of the voice coil type to provide the required amount of hold on the disk. This is accomplished by closely controlling the current through the coil. Again, the correct parameters for a particular type of and size of wafer is entered into the central controller. This provides a highly accurate and repeatable method to lifting the wafers without breakage. In addition, since the wafers are ‘trapped’ within the two posts and finger, no movement can result because of high accelerations during the transportation of the from one processing point to another. 
     Likewise, according to the instant teachings the system can also be implemented using hydraulics with a gas (e.g.; dry air or dry nitrogen) or liquid driven mechanism. The clinching finger motion can be controlled through a device such as a variable needle valve and associated valving, such as by varying the electric current fed to the valve driver or controlling the percent opening of the valves. 
     Overall system control is through a main central processing unit (CPU) which contains the software that defines the actual operations performed. The CPU interfaces with various handling and processing mechanisms through specially designed inter-+faces optimized for the function required. The system as a whole is made up of individual sections representing the various processes. Each section is arranged so as to allow the handling system access. 
     Different environments will, naturally, dictate different arrangements of the various processing sections. This in turn would require different software. To meet the numerous changes in software likely to result, each processing section runs a subprogram in an overall controlling shell. The unique date required by each section is then entered as ‘calibration data’ that is easily passed between the individual sections and the main shelf This allows total flexibility and ease of use since each section is running autonomously with respect to the others. 
     The system above utilizes individual wafer processing sections controlled by a central CPU. Since each section runs autonomously under overall supervision of the shell software, different system arrangements are allowed to meet the needs of the physical environment. 
     The foregoing is meant to illustrate, but not to limit, the scope of the invention. Indeed, those of ordinary skill in the art can readily envision and produce further embodiments, based on the teachings herein, without undue experimentation. 
     For example, while the various components of the system are shown mounted on one side of, or within, the assembly, the invention contemplates locating same on either side or extending off the robot arm end of the assembly. 
     Also, as indicated above, while the invention has been described in relationship to semiconductor wafers, it can be used to handle any flat, stiff sheet like structures of defined dimensions, such as ceramic or glass dishes or plates, petric dishes containing growth media, compact disks in a CD player, removable storage media in a computer system or any other mechanical system which requires removal, transport or handling of disc like articles. Also, various techniques can be used to control the grasping pressure on the wafer. However, the tension is controlled by varying and setting the driving force to the finger  105  and does not require measuring the force actually applied. 
     While the invention is described as having one or two rotating fingers and one or two fixed or moveable (translational) posts, other combinations, or additional posts and or fingers are contemplated. 
     The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiment is to be considered in all respects only as illustrative and not as restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of the equivalence of the claims are to be embraced within their scope.