Abstract:
The present invention is directed to a wafer holder and a related wafer conveyor system. The wafer holder holds a wafer and moves horizontally within a chamber. A contact area between the wafer and the wafer holder is reduced, and potential contaminants generated by ear between components of the wafer holder are trapped by an airtight cover. Since the wafer holder moves horizontally while being fixed to a guide rail, the wafer conveyor system reduces friction between the guide rail and the wafer holder.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention generally relates to an apparatus for use in a semiconductor fabricating process. More specifically, the present invention relates to a wafer holder and a wafer conveyor system equipped with the wafer holder.  
         [0003]     A claim of priority is made to Korean Patent Application No. 2003-95618 filed on Dec. 23, 2003, the disclosure of which is incorporated herein by reference in its entirety.  
         [0004]     2. Description of Related Art  
         [0005]     In a conventional semiconductor fabricating process, an integrated circuit device is fabricated by forming a pattern on a semiconductor wafer, and monitoring the pattern-formed wafer. From a preparation area, a wafer is transferred to an operating area for fabrication and testing. The wafer is placed on an apparatus with its pattern-formed front side or back side facing up depending on the configuration of the fabricating apparatus or the test apparatus. When the wafer&#39;s front side is facing down, edges of the wafer is supported by a wafer holder.  
         [0006]     As shown in  FIG. 1  and  FIG. 2 , a wafer  18  disposed on a wafer holder (not shown) and in a preparation area of a chamber  10  is safely transferred to an operation area  18 ′. A wafer-input opening  14  adapted to load wafer  18  into chamber  10  is formed over the preparation area; a test apparatus  12  adapted to monitor the surface of wafer  18  is installed under the operation area.  
         [0007]      FIG. 2  shows a conventional wafer conveyor system having a pair of parallel guide rails  20  adapted to linearly move a wafer holder. A thread  20   a  is formed on a surface of the respective guide rails  20 . A wafer holder  25  is disposed between guide rails  20 . A base plate  24  of wafer holder  25  has sawtooth-shaped protrusions  24   a  located where base plate  24  and guide rail  20  come in contact. As guide rails  20  rotate, the sawtooth-shaped protrusions  24   a  move in conjunction with thread  20   a . Thus, wafer holder  25  transfers back and forth between the preparation area and the operation area.  
         [0008]     Disposed about its center, base plate  24  has a hollow section  40 . A rotatable supporter ring  26  is provided in hollow section  40 . In the conventional art, a cylindrical roller  30  and a shaft  22  function as a rotating means. Cylindrical roller  30  is horizontally disposed on base plate  24  along the outer perimeter of supporter ring  26 . Shaft  22  is connected along a pivot to rotate roller  30 . Roller  30  is also threaded.  
         [0009]      FIG. 3  illustrates in some additional detail the conventional wafer holder  25 . Wafer holder  25  includes supporter ring  26  and a wafer guide ring  28 . Supporter ring  26  is disposed in hollow section  40 , and wafer guide ring  28  is disposed inside supporter ring  26 . A portion of supporter ring  26  is buried in base plate  24 , but sawtooth-shaped protrusions  26   a  protrude from base plate  24 . Sawtooth-shaped protrusions  26   a  engage the thread of roller  30 . When roller  30  rotates by the driving action of shaft  22 , the thread of roller  30  engages the sawtooth-shaped protrusions  26   a  to rotate supporter ring  26 . A liner  34  is formed along the inner wall of wafer guide ring  28 . The outer edge of wafer  18  is supported by liner  34 . The pattern-formed side of wafer  18  faces down on liner  34 .  
         [0010]     In the conventional wafer conveyor system, when guide rail  20  rotates, sawtooth-shaped protrusions  24   a  move along thread  20   a . Since the movement of wafer holder  25  is perpendicular to the rotational direction of guide rail  20 , friction between the sawtooth-shaped protrusions  24   a  and thread  20   a  causes the respective parts to wear out. If a part is worn out, time is lost in production when the worn out part is maintained or replaced. Furthermore, frictional wear in a system operating within a clean room environment may further cause particle contamination. If metallic particles become attached to a wafer surface, an integrated circuit device formed on the wafer may become defective, or the entire fabrication process may become contaminated.  
       SUMMARY OF THE INVENTION  
       [0011]     In one aspect, the present invention provides a wafer holder to safely support a wafer while reducing the contact area with the wafer.  
         [0012]     In another aspect, the preset invention provides a wafer holder which reduces potential contamination of the wafer.  
         [0013]     In still another aspect, the present invention provides a wafer conveyor system capable of reducing potential contamination of the wafer.  
         [0014]     In order to achieve these aspects, the present invention provides a wafer holder reducing an area of contact between the wafer holder and the wafer. The wafer holder comprises a base plate, a rotatable cylindrical roller, a supporter ring, and a wafer guide ring. The base plate has a circular hollow part and ring-shaped grooves formed along edges of a circular hollow part. The cylindrical roller is adjacent to an outer side of the guide groove to be horizontally installed at the base plate. A thread is formed at a circumferential surface of the cylindrical roller, and a shaft hole is formed at a shaft of the cylindrical hole. The supporter ring is inserted into the guide groove to expose a circumferential surface of the supporter ring to an upper portion of the base plate. Sawtooth-shaped protrusions are formed along the exposed circumferential surface of the supporter ring to gear with the thread of the cylindrical roller. The wafer guide ring is attachably/removably mounted on the supporter ring. A plurality of pads are formed at an inner circumferential surface of the wafer guide ring to support the wafer&#39;s edge.  
         [0015]     The wafer holder may further comprise a cover to prevent particles generated by abrasion of components (or parts) from being scattered. The cover is combined with the base plate to seal the sawtooth-shaped protrusions and cylindrical roller combination from the outside. A hole corresponding to the shaft hole is formed at the cover, so that the cylindrical roller is driven using the shaft. The shaft is connected to the cylindrical roller through the hole of the cover.  
         [0016]     According to another aspect of the present invention, the present invention provides a wafer conveyor system for conveying a wafer in a chamber. The wafer conveyor system comprises driving rollers and passive roller oppositely disposed at both sides of the chamber with a regular space and first and second rails whose inner surface are in contact with the respective driving rollers and passive roller. The first and second rails are oppositely disposed and drive in the same direction. A wafer holder disposed between the first and second guide rails. The first and second guide rails are connected to both sides of the wafer holder to allow the wafer holder to move in parallel with the driving direction of the first and second rails. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  shows a conventional fabrication process system having a wafer conveyor system.  
         [0018]      FIG. 2  shows a conventional wafer conveyor system.  
         [0019]      FIG. 3  is a detail perspective view of a conventional wafer holder.  
         [0020]      FIG. 4  shows a wafer conveyor system according to a preferred embodiment of the present invention.  
         [0021]      FIG. 5  is a top plan view of a wafer conveyor system according to an embodiment of the present invention.  
         [0022]      FIG. 6  is a detail perspective view of the wafer holder according to an embodiment of the present invention.  
         [0023]      FIG. 7  is an exploded view of the wafer holder according to an embodiment of the present invention.  
         [0024]      FIG. 8  is an exploded view of a wafer holder according to another embodiment of the present invention.  
         [0025]      FIG. 9  is a detail perspective view of the wafer holder of  FIG. 8 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     A wafer conveyor system  100  according to the present invention is illustrated in  FIG. 4 . Referring to  FIG. 4 , wafer conveyor system  100  comprises guide rails  152 , further comprises a first guide rail  152   a  and a second guide  152   b . A set of driving rollers  150   a  and a set of passive rollers  150   b  are spaced apart from each other, with each set having one roller disposed in relation to the first guide rail  152   a  and second guide rail  152   b , respectively. The inner portion of guide rails  152   a ,  152   b  contacts and wraps around driving roller  150   a  and passive roller  150   b.    
         [0027]     A wafer holder  110  is disposed between first and second guide rails  152   a ,  152   b , and horizontally moves within a chamber in response to the movement of guide rails  152   a ,  152   b . Namely, wafer holder  110  is transferred between a preparation area and an operation area on conveyor system  100 .  
         [0028]     Wafer conveyor system  100  optionally comprises a plurality of sub-rollers  154  installed between respective combinations of driving roller  150   a  and passive roller  150   b . Sub-rollers  154  help prevent guide rails  152   a ,  152   b  from sagging, thus assisting in the safe movement of wafer holder  110 . Although not illustrated, guide rails  152   a ,  152   b  are preferably flexible, except at those areas where the wafer holder  110  is fixed thereto.  
         [0029]     Wafer holder  110  according to the present invention is fixed to guide rails  152   a ,  152   b . Therefore, contamination generated by wear of guide rails  152   a ,  152   b  and wafer holder  110  is minimized.  
         [0030]     Referring to  FIG. 5 ,  FIG. 6 , and  FIG. 7 , wafer holder  110  includes a base plate  112 , a supporter ring  116 , and a guide ring  118  mounted on an inner portion of the supporter ring  116 . Base plate  112  is mounted on guide rails  152   a ,  152   b . About its center, base plate  112  has a hollow section  140 . A ring-shaped guide groove  134  is formed in base plate  112 . Supporter ring  116  is inserted into guide groove  134 . Sawtooth-shaped protrusions  124  protrude from supporter ring  116  over base plate  112 . Supporter ring  116  rotates along guide groove  134 .  
         [0031]     A cylindrical roller  120  is combined with base plate  112 . A thread  128  is formed on a circumferential surface of cylindrical roller  120 . Cylindrical roller  120  rotates on a shaft  122 , which is horizontally combined with base plate  112 . Rotation of cylindrical roller  120  enables thread  128  to engage sawtooth-shaped protrusions  124 , thus rotating supporter ring  116 . A rotation angle of supporter ring  116  is regulated according to the number of rotations for roller  120 .  
         [0032]     A removable wafer guide ring  118  is engaged with supporter ring  116 . A plurality of pads  130 , which support edges of a wafer, are arranged along an inner circumferential surface of guide ring  118 . Pads  130  further comprise a supporter  130   a  to support the wafer&#39;s edge, and a slide  130   b  to safely guide the wafer onto supporter  130   a . Guide ring  118  is in contact with the wafer&#39;s edge via pads  130 ; therefore, pads  130  prevent materials on edges of a wafer from falling out, because the wafer is not in direct contact with guide ring  116 . In the present invention, supporter ring  116  and cylindrical roller  120  are capsulated by a cover  114 . Cover  114  also prevents contaminants from scattering when sawtooth-shaped protrusions  124  and thread  128  mechanically wear. Cover  114  preferably has a ring-shaped section  114   c , which covers supporter ring  116 , and a housing section  114   h , which extends from ring-shaped section  114   c  to cover cylindrical roller  120 . (See  FIG. 7 ). A cover groove  132  is formed on base plate  112  to secure cover  114 . An insertion hole  126 , wherein shaft  122  of roller  120  is inserted, is formed in housing section  114   h . Roller  120  slides along shaft  122 .  
         [0033]      FIG. 8  is an exploded view of a wafer holder  210  according to a second embodiment of the present invention.  FIG. 9  is a perspective view of wafer holder  210  according to the second embodiment of the present invention.  
         [0034]     Referring to  FIG. 8  and  FIG. 9 , wafer holder  210  according to the second embodiment of the invention includes a supporter ring  216 , and a cover  214 . Cover  214  preferably comprises a ring-shaped section  214   a  to cover supporter ring  216 , and a housing section  214   c , which extends from ring-shaped section  214   a . A cap  214   b  is inserted between a base plate  212  and supporter ring  216 . Housing section  214   c  covers supporter ring  216 , and extends over and covers sawtooth-shaped protrusions  224 . Cover  214  and a supporter ring  218  are inserted into a guide grove  234 , which is formed in base plate  212 . Cover  214  is fixed to guide groove  234 . Supporter ring  216  rotates in conjunction with the rotation of a cylindrical roller  220 . Base plate  212  has a cover groove  232  where housing section  214   c  is inserted therein. Cover groove  232  extends from guide groove  234  to surround a portion containing cylindrical roller  220 . Thus when roller  220  is combined with base plate  212 , housing section  214   c  is combined with groove  232  to cover roller  220 . A thread  228  of roller  220  engages sawtooth-shaped protrusions  224  of supporter ring  216 .  
         [0035]     A removable wafer guide ring  218  engages with supporter ring  216 . A plurality of pads  230  for supporting a wafer&#39;s edge are installed on an inner circumferential surface of guide ring  218 . Pads  230  further comprise a supporter  230   a  to support the wafer&#39;s edge, and a slide  230   b  to safely guide the wafer onto supporter  230   a.    
         [0036]     A wafer is supported by pads  230  of guide ring  218 . Thus, the contact area between the wafer and wafer holder  210  is reduced, thus preventing materials on the wafer from falling down. Slide  230   b  corrects misaligned wafers by guiding the wafers into the correct position along slide  230   b  onto supporter  230   b . Wafer holder  210  rotates a wafer in conjunction with cylindrical roller  220  and supporter ring  216 . Supporter ring  216  and cylindrical roller  220  are sealed from the outside by cover  214 . Cover  214  prevents contaminants from scattering from supporter ring  216  and cylindrical roller  220 .  
         [0037]     While the present invention has been described in detail with reference to the presently preferred embodiments, those skilled in the art will appreciate that various modifications may be made without departing from the scope of the invention. Accordingly, the invention is defined by the following claims.