Abstract:
A latch for securing a wafer to a clamp plate. The latch may include a bearing that couples a wheel to a horizontal shaft. The horizontal shaft is adapted to rotate relative to the clamp ring so that the wheel secures the wafer. The bearing minimizes the amount of particles generated by the moving components of the latch that may contaminant the wafer.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a latch for securing a semiconductor wafer to a clamp ring, weldment or clamp ring for use in a fabrication process.  
           [0003]    2. Background Information  
           [0004]    Integrated circuits are typically fabricated in a flat circular wafer that is cut from an ingot of semiconductor material. Various lithographic, sputtering, etc. processes are performed on the wafer to create the integrated circuits as is known in the art.  
           [0005]    Each wafer is typically secured to a clamp weldment or tab ring of the fabrication equipment by a plurality of latches located about the ring. Each latch may have a roller wheel that is rolled onto the wafer to press the outer wafer edge into the ring. The roller wheel rotates about a horizontal shaft that extends from a latch body. The latch body can swivel about a post that is vertically mounted to the ring. The latch body can be rotated to move the roller wheel between a latched position and an unlatched position.  
           [0006]    Because of high temperatures and the migration of material being sputtered onto the wafer it has been found that the roller wheel will drag and stick when the latch is moved to the latched position. This drag increases friction and may create particles that contaminate the wafer. It would be desirable to provide a wafer clamp that minimizes the amount of roller wheel drag and contaminants produced by the clamp.  
         SUMMARY OF THE INVENTION  
         [0007]    An embodiment of the present invention may include a latch for securing a wafer to a substrate such as a clamp plate. The latch weldment or tab ring of a wafer holder may include a bearing that allows relative movement between a first element and a second element.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of an embodiment of a clamp assembly of the present invention;  
         [0009]    [0009]FIG. 2 is a cross-sectional view of a latch of the assembly;  
         [0010]    [0010]FIG. 3 is an enlarged top view showing a latch rotated relative to a clamp plate;  
         [0011]    [0011]FIG. 4 is a cross-sectional view of an alternate embodiment of a latch.  
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to the drawings more particularly by reference numbers, FIG. 1 shows a wafer holder assembly  10  of the present invention. The wafer holder assembly  10  may be assembled into semiconductor fabrication equipment (not shown). The assembly  10  may secure a wafer  12  during one or more fabrication processes. By way of example, the fabrication process may include oxidation, gaseous deposition, ion implantation, metal deposition, sputtering, electron beam exposure and gaseous etching.  
         [0013]    The wafer holder assembly  10  may include a plurality of latches  14  that are mounted to a clamp plate  16 . Alternatively, the latches may be mounted to a weldment or tab ring (not shown). The latches  14  may be equally spaced about the plate  16  to secure the edges of the wafer  12 . The clamp plate  16  may be assembled into the fabrication equipment.  
         [0014]    [0014]FIG. 2 shows an embodiment of a latch  14 . The latch  14  may include a body  18  that is pivotally connected to a post  20 . The post  20  may be screwed into the clamp plate  16 . The body  18  may include a first horizontal shaft  22  and a second horizontal shaft  24 . The clamp  14  may include a wheel  26  that can rotate about the first horizontal shaft  22 . The wheel  26  may be coupled to the horizontal shaft  22  by a wheel bearing  30 . The wheel bearing  30  may include ball bearings  32  that allow relative movement between the wheel  26  and the shaft  22 . The bearing  32  reduces the friction and amount of particles that can be generated when the wheel  26  rotates about the shaft  22 .  
         [0015]    The bearing  30  can be coupled to the shaft  22  by a pair of clips  34 . The wheel  26  can be coupled to the shaft  22  by clip  36 .  
         [0016]    The latch  14  may include a first roller wheel  38  that is coupled to the first horizontal shaft  22  and a second roller wheel  40  coupled to the second horizontal shaft  24 . The roller wheels  38  and  40  can roll along the clamp plate  16  when the body  18  is rotated about the post  20 . Each roller wheel  38  and  40  may include ball bearings  42  to minimize the frictional contact between the wheels  38  and  40  and the shafts  22  and  24 , respectively. The roller wheels  38  and  40  may be secured to the shafts  22  and  24  by clips  43 .  
         [0017]    The body  18  may be coupled to the post  20  by a spring  44 , a collar  46  and a screw  48 . The spring  48  allows vertical movement of the body  18  and the roller wheels  38  and  40 . The collar  46  may have ball bearings  50  that allow the body  18  to rotate about the post  20 .  
         [0018]    The clamp plate  16  may have a first detent indentation  52  and a second detent indentation  54 . The body  18  can be rotated so that the first roller wheel  38  is located within the first indentation  52 , the second wheel  40  is within the second indentation  54  and the wheel  26  presses the wafer  12 . The first indentation  52  may have a depth that is greater than the second indentation  54  so that the first wheel  38  does not interfere with the wheel  26  pressing onto the wafer  12 .  
         [0019]    Referring to FIG. 3, in operation, each latch  14  is rotated so that the wheels  38  and  40  are not within the indentations  52  and  54 . This allows the wafer  12  to be placed onto the clamp plate  16 . The body  18  is then rotated about the post  20  until the roller wheels  38  and  40  roll into the indentations  52  and  54 , respectively. Rotation of the body  18  also rolls the wheel  26  onto the wafer  12  to secure the same.  
         [0020]    [0020]FIG. 4 shows an alternate embodiment of a clamp  14 ′ wherein the clamp wheel and first roller wheel are integrated into one wheel  60 . The wheel  60  is coupled to a first horizontal shaft  62  by a bearing assembly  64 . The bearing assembly  64  may be sealed by a cap  66 . The roller bearing wheel  60  may have a roller portion  68  that can roll along the clamp plate  16  and a clamp portion  70  that can roll onto the wafer  12 .  
         [0021]    While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.