Patent Publication Number: US-2005136653-A1

Title: Non-adhesive semiconductor wafer holder and assembly

Description:
FIELD OF THE INVENTION  
      The present invention is generally related to semiconductor wafer processing handling systems, and more particularly to devices and methods used for processing semiconductor wafers in a film frame assembly.  
     BACKGROUND OF THE INVENTION  
      Conventional semiconductor wafer handling systems typically utilize semiconductor trays to carry a semiconductor wafer during processing and during inspection of the wafer after processing. Conventionally, a sticky tape is utilized to secure a bottom surface of the semiconductor wafer to the wafer tray during this processing and inspection process. After wafer processing and inspection, the sticky film is exposed to a UV light to remove the sticky tape and adhesive. The semiconductor wafer is thereafter handled using a vacuum coupled to the wafer bottom surface.  
      Semiconductor processing and inspection is an expensive process, and the throughput time for the processing and inspection attributable to handling reduces the number of wafers that can be processed in a given amount of time. Most semiconductor processing fabs run 24 hours 7 days a week. Therefore, reducing the handling time between processing and inspection is an important goal to maximize output of the fab.  
     SUMMARY OF THE INVENTION  
      The present invention achieves technical advantages as a semiconductor wafer holder and process which eliminates the wafer mounting process using sticky tape during processing and inspection. The wafer holder resiliently secures the wafer about its edge, eliminating the need for sticky tape.  
      The wafer holder is adapted to securely receive the semiconductor wafer about its edge, without the use of sticky tape. The insert receives the edges of the semiconductor wafer in a friction fit, and is preferably comprised of a resilient material, such as silicon sponge. The wafer holder has an opening shaped and sized to the semiconductor wafer, and which opening is concentric within the wafer holder. This wafer holder secures the wafer in place during handling and inspection. The wafer holder is assembled to a wafer frame having a perforated film, and only the wafer holder is secured thereto using sticky tape. The sticky tape is later exposed to UV light to remove the sticky tape from the holder. This wafer film is perforated to allow vacuum transmission to the wafer backside.  
      Handling time of a semiconductor wafer using the present invention cuts about 10 minutes off the process time per wafer when processed individually, and cuts about 5 minutes per wafer when processing more than one wafer. This wafer holder and process eliminates the need for more expensive handling systems which is a significant cost advantage over conventional processing. The present invention eliminates the risk of highly potential damage at mounting, as well as reducing the ESD factor. The present invention also reduces potential handling damages when detaching a wafer from the sticky tape, and eases the placing and removing of the wafers with minimal human handling.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a layout diagram of the wafer holder of the present invention received in a standard frame;  
       FIG. 2  is an exploded view of the wafer, wafer holder and standard frame having a perforated film; and  
       FIG. 3  is a flow diagram for processing and handling a wafer using the wafer holder of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring now to  FIG. 1 , there is generally shown at  10  a top view of a layout of the present invention seen to comprise a semiconductor wafer holder  12 . Wafer holder  12  has a concentric opening  14  having a size and profile adapted to securely engage the edge of a semiconductor wafer  16 . The wafer holder  12  is seen to be generally circular, wherein opening  14  has a profile including a flat edge  18  that conforms to the flat edge of the semiconductor wafer  16 . The wafer holder  12  is preferably comprised of a resilient material such as a rubber insert and comprised of a silicon foam material, to provide a resilient edge defining opening  14 . Of course, other resilient materials are suitable which are resilient to securingly engage the perimeter of the semiconductor wafer  14  in an interference fit, and without damage thereto. The wafer holder  12  may also include a bar code label area  20 , and a wand clearance  22 .  
      Referring now to  FIG. 2 , there is shown an exploded view of the semiconductor holder  12  adapted to be received upon a standard wafer frame  30  comprised of a wafer tray. Tray  30  is seen to have a recess for securely receiving the semiconductor holder  12  and has a perforated film  32  extending thereacross with perforations  34  permitting a vacuum to apply a vacuum pressure to the backside of the semiconductor wafer  16 . The outer perimeter of the perforated film  32  includes sticky tape adapted to secure only to the bottom surface of the holder  12 , such that the wafer backside  36  is secured in place with respect to the tray  30  by the secured wafer holder  12 , and not the sticky tape. The semiconductor holder  12  is concentric to the inner frame diameter of holder  30 , as shown. During processing, care is taken to make sure that the tray wafer cavity  30  and base is thoroughly cleaned from particles before using. Proper handling of tray  30  is that it be maintained completely covered when not in use, and is periodically inspected for material integrity.  
      The present invention achieves technical advantages in that the semiconductor wafer  16  is secured with respect to the wafer tray  30  about it periphery edge by the wafer holder  12 , and without the use of any sticky tape. Advantageously, the handling and processing of the semiconductor wafer according to the present invention eliminates three processes, wafer mounting, UV exposure, and manual de-taping of the wafer from sticky tape. Processing time is reduced by approximately 10 minutes per wafer when processed individually, and is reduced by about 5 minutes per wafer when processing more than one wafer. In addition, the present invention eliminates the need for expensive handling systems, and the need for using sticky tape to hold the wafer  16  in place during processing and inspection. In addition, the present invention eliminates the risk of highly potential damage at mounting and de-mounting, and also reduces the ESD factor. Specifically, the present invention eliminates potential handling damages which may occur when removing a wafer from the sticky tape, and eases placing and removing the wafers with minimal human handling. The ease of manufacturing provides a lower processing cost, and a higher processing throughput.  
      Referring now to  FIG. 3  there is shown a conventional process, and  FIG. 4  illustrates a process according to the present invention, the side-by-side comparison showing the eliminated steps of wafer mounting, UV exposure, and manual de-taping of the wafer from sticky tape.  
      Table 1 below illustrates repeatability data for a 150 mm whole wafer tray insert, illustrating that the wafer holder used during processing complies with test perimeters, such as when the standard deviation for each defect measured is under 10.4 um.  
               TABLE ONE                          150 mm WHOLE WAFER TRAY INSERT REPEATABILITY DATA                                                                                                                                 Pass/       Die   Defect   Run I   Run 2   Run 3   Run 4   Run 5   Run 6   Run 7   Run 8   Run 9   Run 10   Average   STDEV   Fail                                                                                 29,44   1   319   313.76   313.76   313.76   313.76   313.76   313.76   313.76   313.76   313.76   314.284   1.65703   Pass       30,46   2   26.59   26.59   26.59   26.59   26.59   26.59   26.59   26.59   26.59   26.59   26.59   3.2E-07   Pass       30,46   3   34.57   34.57   31.91   34-57   34.57   34.57   34.57   34.57   34.57   34.57   34.304   0.84117   Pass       30,46   4   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   0   Pass       30,47   5   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   0   Pass       30,50   6   63.82   63.82   63.82   63.82   63.82   63.82   63.82   61.16   63.82   63.82   63.554   0.84117   Pass       30,50   7   23.93   23.93   23.93   23.93   23.93   23.93   23.93   23.93   23.93   23.93   23.93   0   Pass       31,45   8   31.91   31.91   31.91   29.25   29.25   29.25   29.25   31.91   29.25   29.25   30.314   1.37362   Pass       31,46   9   15.96   15.96   15.96   15.96   15.96   15.96   15.96   15.96   15.96   15.96   15.96   0   Pass       31,48   10   15.95   15.95   15.95   15.95   15.95   15.95   15.95   15.95   15.95   15.95   15.95   0   Pass       32,43   11   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   0   Pass       32,45   12   34.57   34.57   34.57   34.57   34.57   34.57   34.57   34.57   34.57   34.57   34.57   4.5E-07   Pass       32,45   13   63.82   63.82   63.82   63.82   63.82   63.82   63.82   63.82   63.82   63.82   63.82   0   Pass       32,45   14   15.95   15.95   15.95   15.95   15.95   15.95   15-95   15-95   15.95   15.95   15.95   0   Pass       32,46   15   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   0   Pass       33,43   16   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   21.27   0   Pass       33,44   17   18.61   18.61   18.61   15.95   15.95   15.95   15.95   15.95   18.61   18.61   17.28   1.40194   Pass       33,45   18   47.86   47.86   47.86   47.86   47.86   47.86   47.86   47.86   47.86   47.86   47.86   0   Pass       33,45   19   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   10.64   0   Pass       33,45   20   26.59   26.59   23.93   26.59   26.59   26.59   26.59   23.93   26.59   26.59   26.058   1.12155   Pass                 This test passes if the standard deviation for each defect measured is under 10.4 um. Therefore this test Is successful.            This tray can be used to Inspect all 6″ whole wafers as applicable.             
 
      Though the invention has been described with respect to a specific preferred embodiment, many variations and modifications will become apparent to those skilled in the art upon reading the present application. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.