Abstract:
A wafer alignment platform serves to align a wafer so as to make the wafer be carried by a vacuum device that is vertically movable and revolvable. A laser detecting device detects a positioning mark on the wafer and aligns the positioning mark to a directional mark so as to automatically perform center alignment and orientation of the wafer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to devices used in semiconductor processes, and more particularly, to a wafer alignment platform that utilizes a referential notch preformed on a wafer edge to automatically align the wafer. 
         [0003]    2. Description of Related Art 
         [0004]    In semiconductor processes, automatized devices are usually implemented to load wafers into various reaction/process chambers (hereinafter referred to as the process chambers) to receive processes. A typical automatized device for such application is a robot arm serving to keep accurately transporting wafers. The robot arm is installed in a transportation chamber and capable of getting in and out one or more process chambers adjacent to the transporting chamber. For maximizing the wafer processing efficiency, it is very important to precisely place a wafer at an optimum position in the process chamber. In view of this, precise location of a center of a wafer and accurate orientation of the wafer at its initial position help the robot arm to correctly move the wafer to the process chamber and place the wafer at the optimum position in the process chamber. 
         [0005]    According to known arts for determining a location of a center of a wafer and an orientation of the wafer at the wafer&#39;s initial position is to manually align a referential notch formed at an edge of the wafer to a directional mark under naked-eye observation. However, this approach tends to suffer from visual errors. Meantime, this approach provides no solution to accurately rotate a wafer to a specific angle for meeting need of subsequent processes. Hence, the conventional approach is not perfect enough to the optimum yield and efficiency of wafer process. 
       SUMMARY OF THE INVENTION 
       [0006]    One objective of the present invention is to provide a wafer alignment platform that utilizes a referential notch preformed at an edge of a wafer as a positioning mark to automatically align the wafer so as to realize center alignment and full orientation of the wafer on the platform and in turn facilitate a robot arm in correctly moving the wafer to a process chamber and placing the wafer at an optimum position in the process chamber. 
         [0007]    To achieve the aforesaid objective, the wafer alignment platform of the present invention comprises: 
         [0008]    a vacuum device, serves to hold a wafer on a shaft that is vertically movable and revolvable; 
         [0009]    an aligning device that aligns a center of the wafer to a center of the shaft; 
         [0010]    a controlling device, driving the shaft to move vertically and revolve; and 
         [0011]    a laser detecting device, detecting a positioning mark of the wafer as well as a revolving angle of the wafer and converting the detected positioning mark and revolving angle into electrical signals, wherein the laser detecting device is further coupled with the controlling device so that the controlling device is controlled by the electrical signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a perspective view of a wafer alignment platform according to the present invention; 
           [0014]      FIG. 2  is a lateral view of the wafer alignment platform according to the present invention; 
           [0015]      FIG. 3  is a schematic drawing showing a wafer being aligned on the wafer alignment platform according to the present invention; 
           [0016]      FIG. 4  is another schematic drawing showing the wafer being aligned on the wafer alignment platform according to the present invention; and 
           [0017]      FIG. 5  is yet another schematic drawing showing the wafer being aligned on the wafer alignment platform according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    While a preferred embodiment is provided herein for illustrating the concept of the present invention as described above, it is to be understood that the components in these drawings are made for better explanation and need not to be made in scale. Moreover, in the following description, resemble components are indicated by the same numerals. 
         [0019]    Referring to  FIGS. 1 ,  2  and  3 , a wafer alignment platform according to the present invention primarily comprises a vacuum device  30 , an aligning device  4 , a controlling device  1 , and a laser detecting device  5 . 
         [0020]    The vacuum device  30  serves to hold a wafer  90  on a shaft  2  that is vertically movable and revolvable. 
         [0021]    The aligning device  4  serves to align a center of the wafer  90  to a center of the shaft  2 . 
         [0022]    The controlling device  1  serves to drive the shaft  2  to move vertically and revolve. 
         [0023]    The laser detecting device  5  serves to detect a positioning mark as well as a revolving angle of the wafer  90  and convert the detected positioning mark and revolving angle into electrical signals. Furthermore, the laser detecting device  5  is coupled with the controlling device  1  so that the controlling device  1  is controlled to revolve by the electrical signals. 
         [0024]    As can be seen in the drawings, the shaft  2 , vacuum device  30 , aligning device  4 , controlling device  1 , and the laser detecting device  5  are integrated on a platform  8 . 
         [0025]    According to the preferred embodiment as shown, the shaft  2  is substantially a cylinder lever of an elevating device  20  such as an air cylinder or a hydraulic cylinder. The controlling device  1  is a torque motor  10 . The elevating device  20  is mounted on a driving shaft of the motor  10  so that the driving shaft of the motor  10  drives the elevating device  20  to revolve, thereby making the shaft  2  move vertically or revolve. 
         [0026]    The vacuum device  30  provides a sucker  31  that is settled on the shaft  2  for holding the wafer  90 . Thereupon, the shaft  2  of the elevating device  20 , the motor  10  and the vacuum device  30  jointly move the wafer  90  up and down, and revolve wafer  90  so as to settle the wafer  90  in position. 
         [0027]    The aligning device  4  is constructed from a plurality of positioning rods  41  that are erected and arrayed on the platform  8  as a circle surrounding the sucker  31 . Each said positioning rod  41  has a top thereof formed as an inclined plane  42  inclined toward a center of the sucker  31  so that the inclined planes  42  of the circularly arrayed positioning rods  41  can fittingly support the wafer  90  at an edge  91  of the wafer  90 . 
         [0028]    The laser detecting device  5  is settled corresponding to the edge  91  of the wafer  90  for detecting a referential notch preformed on the edge  91  of the wafer  90  as a positioning mark and determining a revolving angle of the wafer  90  basing on the referential notch. 
         [0029]    The torque motor  10 , elevating device  20 , vacuum device  30  and laser detecting device  5  function systematically so as to align the wafer  90  efficiently. The process of wafer alignment will be given below with reference to  FIGS. 3 through 5 . 
         [0030]    As can be seen in  FIG. 3 , the wafer alignment platform is in a standby state. The elevating device  20  props up the vacuum device  30  and the sucker  31  so as to hold the sucker higher than the tops of the positioning rods  41 . A known robot arm places a wafer  90  on the sucker  31  with an obverse side of the wafer  90  upward. At present, the vacuum device  30  is not started and the wafer  90  is not caught by the sucker  31 . 
         [0031]    Referring to  FIG. 4 , the elevating device  20  brings the vacuum device  30  and the sucker  31  downward so that the inclined planes  42  of the circularly arrayed positioning rods  41  support the wafer  90  at its edge  91 . Therefore, the centripetally inclined planes  42 , in virtue of the gravity, naturally guide the center of the wafer  90  to align to the center of the shaft  2 . 
         [0032]    According to  FIG. 5 , when the vacuum device  30  is started, the sucker  31  catches and holds the wafer  90 . The elevating device  20  pushes the wafer  90  upward to holds the wafer  90  higher than the tops of the positioning rods  41 . Then the torque motor  10  rotates the elevating device  20  and sucker  31 . Afterward, the laser detecting device  5  detects the referential notch at the edge  91  of the wafer  90  and converts the detected data into electrical signals. When receiving the electrical signals, the torque motor  10  stops and thus the wafer alignment process is complete. 
         [0033]    At the completion of the wafer alignment process, the vacuum device  30  disables the sucker  31  from catching the wafer  90  so as to allow the robot arm to move the aligned wafer  90  to a process chamber for further processes. Since the wafer has been properly oriented on the wafer alignment platform, the robot arm can correctly move the wafer  90  to the process chamber and rightly place the wafer at the optimum position in the process chamber. 
         [0034]    Although the particular embodiment of the invention has been described in detail for purposes of illustration, it will be understood by one of ordinary skill in the art that numerous variations will be possible to the disclosed embodiment without going outside the scope of the invention as disclosed in the claims.