Abstract:
A vacuum chuck is disclosed for holding and positioning wafers more stably and securely. The vacuum chuck includes a supporting assembly having a receiving groove and at least one first vacuum aperture defined in the receiving groove. A seal unit includes a seal ring bulging to form a vacuum trough. The seal ring is fixed in the receiving groove of the supporting assembly and has at least one second vacuum aperture communicating with the first vacuum aperture. A chuck connector fastened with the supporting assembly has at least one vacuum port and at least one vacuum orifice communicating with the vacuum port. At least one vacuum hose connects the first vacuum aperture, the second vacuum aperture with the vacuum orifice and the vacuum port of the chuck connector for evacuating the air of the vacuum trough to hold and position the wafer on the seal ring and the supporting assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a national stage application of PCT/CN2012/073175, filed on Mar. 28, 2012. This application claims the benefit and priority of this prior application and incorporates the disclosure of this prior application by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a chuck for holding and positioning semiconductor workpieces during various processing procedures, and more particularly relates to a vacuum chuck for holding and positioning the semiconductor workpieces more stably and securely. 
     2. The Related Art 
     In a semiconductor device manufacturing process, semiconductor workpieces such as wafers need to undergo various processing procedures. The wafers are usually held and positioned on a chuck to be processed and the chuck is an important device in the semiconductor device manufacturing process. 
     With the development of semiconductor technology, the chuck is improved gradually for satisfying the requirement of the various processing procedures. The chucks are divided into two kinds. One kind is a contact type chuck and the other kind is a non-contact type chuck. A vacuum chuck which holds and positions the wafer thereon by vacuum drawing force is a typical contact type chuck. Referring to U.S. Pat. No. 6,032,997 discloses a vacuum chuck. The vacuum chuck has a body portion. The body portion defines a top surface. A plurality of concentric flat lands are disposed on the top surface. Between every two adjoining lands, a concentric trench is defined. Several orifices are defined to pass through the body portion and communicate with the trenches respectively. Each orifice is connected to a vacuum hose which is connected to a vacuum source. The wafer contacts the lands and then the air is evacuated from the trenches. Lastly, the wafer is held on the lands of the vacuum chuck by the vacuum drawing force. 
     Another vacuum chuck is published in U.S. Pat. No. 6,164,633. The vacuum chuck has a generally square body. The body has a first surface and a second opposing surface. The first surface has a first circular platform and a second circular platform for receiving two different diameter wafers. The second surface has a third circular platform for receiving a wafer having a third diameter. A first vacuum trough and a second vacuum trough are respectively formed in the first platform and the second platform. A third vacuum trough is formed in the third platform. Three vacuum passageways are formed and extend from the interior portions of the body to three exterior vacuum ports located at one side of the body. Each vacuum passageway corresponds to a single vacuum trough and links the respective vacuum trough to a vacuum source and so that the air is evacuated from the vacuum trough to hold the wafer on the corresponding platform. 
     However, the two vacuum chucks disclosed above have very weak airtightness, which easily causes the wafer held thereon to come off the vacuum chuck and damage the wafer. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a vacuum chuck for holding and positioning wafers more stably and securely. In an exemplary embodiment, the vacuum chuck includes a supporting assembly having a first receiving groove and a second receiving groove. At least one first vacuum aperture is defined in the first receiving groove. The supporting assembly has a vacuum passageway encircled by the second receiving groove. A first seal unit and a second seal unit are respectively fixed in the first receiving groove and the second receiving groove of the supporting assembly. The first seal unit includes a first seal ring bulging to form a vacuum trough. The first seal ring is fixed in the first receiving groove and has at least one second vacuum aperture communicating with the first vacuum aperture. The second seal unit includes a second seal ring fixed in the second receiving groove. A chuck connector fastened with the supporting assembly has at least one vacuum port and at least one vacuum orifice communicating with the vacuum port. The chuck connector has a vacuum passageway communicating with the vacuum passageway of the supporting assembly for evacuating the air enclosed by the second seal ring and the wafer. At least one vacuum hose connects the first vacuum aperture, the second vacuum aperture with the vacuum orifice and the vacuum port of the chuck connector for evacuating the air of the vacuum trough to hold and position the wafer on the seal rings and the supporting assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
         FIG. 1  is a top view of a vacuum chuck in accordance with the present invention; 
         FIG. 2  is a bottom view of the vacuum chuck; 
         FIG. 3  is a top view of a supporting body of the vacuum chuck; 
         FIG. 4  is a bottom view of the supporting body of the vacuum chuck; 
         FIG. 5  is a top view of a middle plate of the vacuum chuck; 
         FIG. 6  is a bottom view of the middle plate of the vacuum chuck; 
         FIG. 7  is a top view of a bottom pedestal of the vacuum chuck; 
         FIG. 8  is a bottom view of the bottom pedestal of the vacuum chuck; 
         FIG. 9  is a cross-sectional view of a supporting assembly assembling with a chuck connector of the vacuum chuck; 
         FIG. 10  is a cross-sectional view of the vacuum chuck; 
         FIG. 11  is another cross-sectional view of the vacuum chuck; 
         FIG. 12  is an exploded view of a first seal unit and a second seal unit of the vacuum chuck; 
         FIG. 13  is a perspective view of a connecting head of the vacuum chuck; 
         FIG. 14  is a perspective view of the chuck connector of the vacuum chuck; and 
         FIG. 15  is a cross-sectional view of the chuck connector. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 to 11 , a vacuum chuck  100  of the present invention will be described in detail with reference to the accompanying drawings. The vacuum chuck  100  is substantially circular. The vacuum chuck  100  includes a supporting assembly  10  and a chuck connector  20  coupled with each other. The supporting assembly  10  includes a supporting body  11 , a bottom pedestal  13  and a middle plate  12  disposed between the supporting body  11  and the bottom pedestal  13 . The supporting body  11 , the middle plate  12  and the bottom pedestal  13  are fastened together through screws in the preferred embodiment. Without doubt, there are other ways to fasten the supporting body  11 , the middle plate  12  and the bottom pedestal  13  together. 
     The supporting body  11  is in disk-shape and has a body portion  111  and a sidewall  112  protruding downwardly from the edge of the body portion  111 . The body portion  111  and the sidewall  112  define a receiving portion  113  to receive the middle plate  12  and the bottom pedestal  13 . The center of the body portion  111  defines a circular mating hole  114  wherein the chuck connector  20  is fixed. The body portion  111  defines four locating holes  115  passing therethrough. A top surface of the body portion  111  defines four holding trenches  116 . One end of each holding trench  116  communicates with the corresponding locating hole  115 , and the other end of each holding trench  116  communicates with the mating hole  114 . The four locating holes  115  and the four holding trenches  116  are distributed on the body portion  111  symmetrically. 
     The middle plate  12  is a circular plate and has a first aligning hole  121  at the center thereof. A first vacuum passageway  122  is defined on the middle plate  12  and adjoining the first aligning hole  121 . The middle plate  12  has first spindle holes  123  and first fixing holes  124 . Preferably, there are three first spindle holes  123  and three first fixing holes  124 , and the first spindle holes  123  and the first fixing holes  124  are distributed alternately and around the first aligning hole  121  and the first vacuum passageway  122 . A top surface and a bottom surface of the middle plate  12  respectively define a circular recess  125  encircling the first aligning hole  121 , the first vacuum passageway  122 , the first spindle holes  123  and the first fixing holes  124 . Two seal members  30  are fixed in the recesses  125  respectively for sealing the juncture place between the middle plate  12  and the chuck connector  20 , and the juncture place between the middle plate  12  and the bottom pedestal  13 , avoiding the air entering into the vacuum chuck  100 . 
     The bottom pedestal  13  is in circular-shape and has a top surface and a bottom surface holding a wafer which needs to be processed. The top surface of the bottom pedestal  13  defines a circular hollow portion  130  at the center thereof for receiving the middle plate  12  therein. The bottom surface of the bottom pedestal  13  defines a first receiving groove  131  and a second receiving groove  132 . The two receiving grooves  131 ,  132  are circular and concentric. The diameter of the first receiving groove  131  is greater than the diameter of the second receiving groove  132 , which means the first receiving groove  131  is located near the edge of the bottom surface of the bottom pedestal  13  and the second receiving groove  132  is located near the center of the bottom surface of the bottom pedestal  13 . Both the first receiving groove  131  and the second receiving groove  132  define a plurality of screw holes  133 . The first receiving groove  131  defines four first vacuum apertures  134  distributed symmetrically and passing through the bottom pedestal  13 . The bottom surface between the first receiving groove  131  and the second receiving groove  132  defines a plurality of interconnected air slots  135 . Three pressure releasing holes  140  are symmetrically defined in the air slots  135  for releasing the vacuum drawing force between the first receiving groove  131  and the second receiving groove  132  when the wafer is taken away from the vacuum chuck  100 . The center of the bottom pedestal  13  has a second aligning hole  136 . A second vacuum passageway  137  is defined and passes through the bottom pedestal  13  and adjoining the second aligning hole  136 . Three second spindle holes  138  and three second fixing holes  139  pass through the bottom pedestal  13 . The second spindle holes  138  and the second fixing holes  139  are distributed alternately and around the second aligning hole  136  and the second vacuum passageway  137 . The second aligning hole  136 , the second vacuum passageway  137 , the second spindle holes  138  and the second fixing holes  139  are surrounded by the second receiving groove  132 . The bottom surface of the bottom pedestal  13  surrounded by the second receiving groove  132  defines a plurality of the air slots  135  communicating with the second vacuum passageway  137 . 
     Please refer to  FIG. 12  as well as  FIGS. 9 to 11 . A first seal unit  40  and a second seal unit  50  of the vacuum chuck  100  is illustrated. The first seal unit  40  includes a pair of first metal rings  41  and a first seal ring  42 . The middle of the first seal ring  42  bulges to form a vacuum trough  421 , and one of the first metal rings  41  is disposed in the vacuum trough  421 . The pair of first metal rings  41  and the first seal ring  42  are fixed together through screws, and the first seal ring  42  is disposed between the pair of first metal rings  41 . The first seal unit  40  is assembled in the first receiving groove  131  of the bottom pedestal  13  by inserting screws in the screw holes  133 . Either of the first metal rings  41  and the first seal ring  42  have four second vacuum apertures  43  corresponding to the four first vacuum apertures  134  of the bottom pedestal  13 . The second seal unit  50  includes a pair of second metal rings  51  and a second seal ring  52 . The pair of second metal rings  51  are located at both sides of the inner edge of the second seal ring  52 . The pair of second metal rings  51  and the inner edge of the second seal ring  52  are fixed together through the screws, and the inner edge of the second seal ring  52  is disposed between the pair of second metal rings  51 . The second seal unit  50  is assembled in the second receiving groove  132  of the bottom pedestal  13  by inserting the screws in the screw holes  133 . According to the requirement of different process operations, the first seal ring  42  and the second seal ring  52  can be made of any suitable material, such as rubber. 
     With reference to  FIG. 13  as well as  FIGS. 9 to 10 , a connecting head  60  of the vacuum chuck  100  is illustrated. The connecting head  60  is hollow and substantially L-shaped. One end of the connecting head  60  has screw threads and is located in the corresponding first vacuum aperture  134  of the bottom pedestal  13 . The other end of the connecting head  60  is substantially cone-shaped and is disposed in the corresponding locating hole  115  of the supporting body  11  to be inserted into a vacuum hose  70  which is received in the holding trench  116  of the supporting body  11 . There are four connecting heads  60  and four vacuum hoses  70  to mate with the four first vacuum apertures  134  of the bottom pedestal  13 , and the four locating holes  115  and the four holding trenches  116  of the supporting body  11  respectively. 
     Please refer to  FIGS. 14 to 15  as well as  FIGS. 1, 9, 10, 11 . The chuck connector  20  defines two parallel elongated vacuum ports  21  on a top surface thereof. A sidewall of the chuck connector  20  defines four vacuum orifices  22 . The four vacuum orifices  22  communicate with the two vacuum ports  21  respectively. A bottom surface of the chuck connector  20  defines a third aligning hole  23  at the center thereof. A third vacuum passageway  24  is defined and adjoining the third aligning hole  23  and passes through the chuck connector  20 . Three third spindle holes  25  and three third fixing holes  26  are defined on the bottom surface of the chuck connector  20 . The third spindle holes  25  and the third fixing holes  26  are distributed alternately and around the third aligning hole  23  and the third vacuum passageway  24 . Two elongated seal elements  80  are provided and installed around the vacuum ports  21  for seal function when the chuck connector  20  is coupled with a vacuum source (not shown). The chuck connector  20  is fixed in the mating hole  114  of the supporting body  11  and is fastened with the middle plate  12  and the bottom pedestal  13  through inserting the screws in the first, second and third fixing holes  124 ,  139 ,  26 . Three spindles (not shown) are installed in the first, second and third spindle holes  123 ,  138 ,  25 . An aligning tool is located in the first, second and third aligning hole  121 ,  136 ,  23  for aligning the wafer on the vacuum chuck  100 . 
     The vacuum chuck  100  in using, the bottom surface of the bottom pedestal  13  contacts with a wafer. More specifically, the first seal ring  42  contacts with the outer edge part of the wafer and the air in the vacuum trough  421  is evacuated from the vacuum apertures  43 ,  134 , the connecting heads  60 , the vacuum hoses  70 , the vacuum orifices  22  and the vacuum ports  21  successively. The second seal ring  52  contacts with the middle part of the wafer and the air enclosed by the second seal ring  52  and the wafer is evacuated from the air slots  135  and the vacuum passageways  137 ,  122 ,  24 . Then the wafer is held and positioned on the vacuum chuck  100  stably and securely. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.