Patent Document

FIELD OF THE INVENTION 
   The present invention relates to a wafer transfer apparatus and, more particularly, to a wafer transfer apparatus having cylinder-driving movable fingers. 
   BACKGROUND OF THE INVENTION 
   Semiconductor wafers are transferred to locations where processes (e.g., cleaning, deposition, etching, etc.) are carried out. Therefore, various wafer transfer apparatuses have been used. 
   Generally, wafer transfer apparatuses used at an atmospheric pressure fix substrates using vacuum. Since a wafer transfer apparatus used in a high vacuum system cannot use vacuum, a shoe is mounted on front and rear edges of a plate on which a wafer is placed. Thus, wafers may be separated from blades when they are transferred at a high speed. Further, there was no method for correcting wafers that are disposed to swerve from blades. 
   In recent years, means for clamping wafers placed on blades have been developed so as to fix the wafers stably. Nevertheless, the clamping means has a complex structure and thus it is hard to regulate the structure of the clamping means. Moreover, wafers may be damaged by the clamping means. 
   SUMMARY OF THE INVENTION 
   A feature of the present invention is to provide a wafer transfer apparatus which transfers wafers in a high-vacuum chamber at a high speed and corrects locations of swerving wafers. 
   Another feature of the present invention is to provide a wafer transfer apparatus which prevents breakage of held wafers. 
   Further another feature of the present invention is to provide a wafer transfer apparatus having a simple structure. 
   Still another feature of the present invention is to provide a wafer transfer apparatus which checks whether In order to achieve these features, the present invention provides a wafer transfer apparatus includes a robot arm unit whose operation is controlled by driving means, a blade on which a wafer is placed, and a clamping member for locating the wafer placed on the blade in position while fixing the wafer. The blade is installed at the end of the robot arm unit, and the clamping is installed at the blade. 
   In some embodiments, the blade includes a fix finger. The clamping member includes a moving pusher for pushing the wafer placed on the blade toward the fix finger, a driving part for slidingly moving the moving pusher, and a case where the driving part is installed. 
   In some embodiments, the driving part comprises a pneumatic cylinder. 
   In some embodiments, the wafer transfer apparatus further includes a sensing unit for sensing the location of the pneumatic cylinder to determine whether wafers are held normally or separated. 
   In some embodiments, the location of the pneumatic cylinder is divided into standby, holding, and separating sections. The sensing unit includes a first sensor for sensing whether the cylinder is in the standby section, a second sensor for sensing that the cylinder is separated from the holding section to be in the separating section, and a third sensor for sensing whether a wafer is placed on the blade. 
   In some embodiments, the moving pusher includes a connecting rod connected to a moving axis of the driving part, a pair of supporters extending from both sides of the connecting rod, and a movable finger contacting the edge of a wafer to support the wafer. The movable finger is installed at the pair of the supporters. The clamping means further includes at least one stopper for regulating a moving distance of the moving pusher. 
   In some embodiments, the stopper is coupled with the case like a screw. The location of the stopper may be regulated. 
   In some embodiments, the wafer transfer apparatus further includes a spring for controlling a moving speed of the moving pusher to absorb a shock produced when the moving pusher contacts the wafer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top plan view of a wafer transfer apparatus according to the present invention. 
       FIG. 2  is a perspective view of a blade illustrated in  FIG. 1 . 
       FIG. 3  is a top plan view of the blade illustrated in  FIG. 1 . 
       FIG. 4  is a side view of the blade illustrated in  FIG. 1 . 
       FIG. 5  shows steps of regulating a wafer centering while movable fingers of a moving pusher move forward. 
       FIG. 6  shows the example that a forward-moving distance of a moving pusher is regulated using a stopper. 
       FIG. 7  shows a hydraulic cylinder in which first and second sensors are installed. 
       FIG. 8  is a table for explaining a method of determining whether a wafer using sensors of a sensing unit is normal. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     FIG. 1  is a top plan view of a wafer transfer apparatus according to the present invention, and  FIG. 2  through  FIG. 4  are views for explaining a configuration of a blade illustrated in  FIG. 1 . 
   As illustrated in  FIG. 1 , a wafer transfer apparatus  100  has a robot arm unit  110  and a blade  120 . The operation of the robot arm unit  110  is controlled by driving means (not shown) such as, for example, stepping motor. A semiconductor wafer  200  is placed on the blade  120 . 
   The blade  120  is fixedly coupled to a terminal of the robot arm unit  110 . 
   Referring to  FIG. 1  through  FIG. 4 , the blade  120  is Y-shaped in general and has a coupling part  122  and a pair of wings  124 . The coupling part  122  is coupled to a terminal of the robot arm unit  110 . The wing  124  topers away from the coupling part  122  to the end of the wing  124 . A fix finger  128  is installed at the end of the wing  124 . Four support protrusions  126  are mounted on the wing  124  to support the bottom of a wafer. 
   The coupling part  122  has a clamping member  130  for stably clamping wafers onto the wing  124  and a sensing unit  150  for determining whether the wafers are normal. 
   The clamping member  130  places the wafer “W” in position while fixing the same and includes a moving pusher  134 , a pneumatic cylinder  132  acting as a driving part, and a case  131 . 
   The moving pusher  134  pushes a wafer “W” placed on the blade  120  toward the fix finger  128  and has a connecting rod  136  connected to a moving axis  133 a of the pneumatic cylinder  132  and a pair of supporters  138  extending from both sides of the connecting rod  136 . A movable finger  140  is installed at the end of the supporter  138  to be in contact with the edge of a wafer. 
   The moving pusher  134  is fully moved backward by the pneumatic cylinder  132 . If not, a misaligned wafer may collide with the moving pusher  134  when being placed on the blade  120 . The moving pusher  134  is moved forward by the pneumatic cylinder  132 . At the forward-moving location of the moving pusher  134 , the movable finger  140  and the fix finger  128  are in contact with the edge of a wafer to support the wafer. As illustrated in  FIG. 5 , if a wafer “W” is erroneously placed on the blade  120  (the center of the wafer “W” swerves slightly), movable fingers of the moving pusher  134  move forward to regulate a centering of the wafer “W”. 
   The clamping member  130  has a stopper  142  for regulating a moving distance (moving-toward distance) “L” of the moving pusher  134 . The stopper  142  is installed in the case  131  to regulate a moving-toward distance of the moving pusher  134 . Particularly, the stopper  142  is coupled with the case  131 , like a screw, to regulate the forward-moving distance of the moving pusher  134 , if necessary. The location of the stopper  142  must be regulated because the clamping location of a wafer may vary with a degree of expansion and contraction of the wafer.  FIG. 6  shows the example that a forward-moving distance of a moving pusher is regulated using a stopper. 
   The clamping member  130  has a spring  144  for shock absorption. The spring  144  is installed at a connecting rod  136  of the moving pusher  134 , absorbing a shock applied to a wafer when the moving pusher  134  moves forward to be in contact with the wafer. 
   According to the present invention, the wafer transfer apparatus may prevent a wafer damage that may occur while holding the wafer. Preventing the wafer damage may be accomplished through the steps as follows: (1) a speed of the moving pusher  134  may be controlled using a pneumatic cylinder; (2) the speed of the moving pusher  134  may be reduced using a spring  144 ; and (3) a forward-moving location of the moving pusher  134  is regulated using a stopper  142 . 
   Referring to  FIG. 3  and  FIG. 7 , the sensing unit  150  has first to third sensors  152 ,  154 , and  156 . The first and second sensors  152  and  154  sense the location of a pneumatic cylinder, and the third sensor  156  detects whether a wafer “W” is placed on a blade  120 . The wafer transfer apparatus  100  according to the invention may check whether wafers are normal, using the sensors  152 ,  154 , and  156 . As illustrated in  FIG. 7 , the location of the pneumatic cylinder  132  is divided into a standby section “a”, a holding section “b”, and a separating section “c”. The first sensor  152  senses a cylinder disposed at the standby section “a”, and the second sensor  154  senses a cylinder disposed at the separating section “c”. As illustrated in  FIG. 8 , a sensing unit determines whether wafers are normal or abnormal (standby normal, standby abnormal, holding normal, holding broken, and holding separated). 
   In the present invention, the above-mentioned wafers include substrates for a reticle, display panel substrates such as substrates for liquid display panel and substrates for plasma display panel, substrates for hard disk, and wafers for electronic devices such as semiconductor devices. 
   As explained so far, wafers incorrectly placed on blades are corrected (regulated in position) to precisely move to the next location. Since wafers are physically supported (held) at four or more points, they are transferred at a high speed and do not drop. Further, a plurality of sensors are used to sense whether wafers are broken or separated. 
   Other modifications and variations to the invention will be apparent to a person skilled in the art from the foregoing disclosure. Thus, while only certain embodiment of the invention has been specifically described herein, it will be apparent that numerous modifications may be made thereto without departing from the spirit and scope of the invention.

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