Abstract:
A semiconductor manufacturing apparatus includes a wafer support having a grinding base on which a wafer is disposed, and a grinding assembly disposed above the grinding base. The grinding assembly includes a grinding plate having grinding projections at the bottom thereof and at least two fixing pins protruding at a the top thereof, and a grinding mount to which the grinding plate to which the grinding plate can be initially coupled and then secured to quickly. The grinding mount has first fixing grooves in a bottom surface thereof and in which the respective fixing pins are inserted and held. A vacuum system and/or mechanical fasteners are used to then secure the grinding plate to the grinding mount.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a process of grinding the back of a wafer in the manufacturing of a semiconductor device. More particularly, the present invention relates to grinding apparatus for grinding the back of a semiconductor wafer and to a method of fixing a grinding plate in an assembly of the grinding apparatus.  
         [0003]     2. Description of the Related Art  
         [0004]     A semiconductor wafer is subjected to a back grinding process after a device is formed on the semiconductor wafer and before the device is packaged. The back grinding process includes attaching a tape to and over the front of the wafer, subsequently grinding the back of the wafer, and then removing the tape from the front of the wafer. This so-called back grinding process is performed to reduce the thickness of the wafer enough so that the resulting structure can be assembled in a package.  
         [0005]     The apparatus for carrying out the back grinding process includes a support for stably supporting a semiconductor wafer, and a grinding assembly disposed above the support and capable of grinding the back side of the semiconductor wafer. The grinding assembly includes a grinding mount, a grinding plate attached to a lower portion of the grinding mount for grinding the back side of the semiconductor wafer, and a driving motor connected to the grinding mount via a rotary shaft for rotating the grinding plate.  
         [0006]      FIG. 1A  and  FIG. 1B  illustrate a conventional grinding assembly  30  of semiconductor wafer back-grinding apparatus. Referring to these figures, a grinding mount  20  is provided with a plurality of bolt holes  24  into which bolts  22  are inserted. A grinding plate  10  has threaded holes  12  in the top thereof at locations corresponding to the locations of the bolt holes  24 . The bolts  22  extend through the bolt holes  24  and are threaded to the grinding plate  10  within the corresponding threaded holes  12 , respectively. A driving motor (not shown) is connected to the grinding mount  20  by a rotary shaft  26  to rotate the grinding plate  10 . Reference numeral  14  designates grinding projections which grind the back side of the semiconductor wafer.  
         [0007]     In order to attach the grinding plate  10  to the grinding mount  20 , the grinding plate  10  must first be aligned with the bottom of the grinding mount  20 . Then the grinding plate  10  is fastened to the grinding mount  20  with the bolts  22 . In this case, however, the forces exerted by the bolts  22  on the grinding plate may differ, thereby making it difficult to properly level the grinding plate  10 , i.e., thereby making it difficult to ensure that the tips of the grinding projections  14  all lie in a horizontal plane. That is, it is time-consuming to accurately position the grinding plate  10  relative to a wafer when fastening the grinding plate  10  to the grinding mount  20 .  
       SUMMARY OF THE INVENTION  
       [0008]     An object of the present invention is to provide a grinding apparatus having a grinding assembly in which a grinding plate can be quickly mounted in a precise position to a grinding mount.  
         [0009]     Likewise, an object of the present invention is to provide a method of fastening a grinding plate to a grinding mount of grinding apparatus, which can be carried out in a short amount of time and yet wherein the grinding plate is positioned precisely in the grinding apparatus.  
         [0010]     According to one aspect of the present invention, there is provided a grinding assembly including a grinding plate having grinding projections at the bottom thereof and at least two fixing pins protruding at the top thereof, and a grinding mount having at least two first fixing grooves in a bottom surface thereof, at least two second fixing grooves in the bottom surface, and first guide grooves extending in the bottom surface along respective arcs of a circle. Each of the first guide grooves connects a respective one of the first fixing grooves to a respective one of the second fixing grooves.  
         [0011]     Each of the fixing pins may have a spherical coupling projection at the top thereof. In addition, annular rubber packings are fixed on walls of the grinding mount which define the sides of the second fixing grooves, respectively. Each of the packings has an inner diameter smaller than the diameter of the second fixing groove and smaller than the diameter of the coupling projection received in the second fixing groove. Thus, the packings can hold the fixing pins within the second fixing grooves.  
         [0012]     The fixing pins lie along a circle having a radius equal to that of the circle along which the first guide grooves extend, and the fixing pins are spaced from each other along that circle by equal distances. The second fixing grooves may be deeper than the first fixing grooves, and the fixing projections may have a height substantially equal to the depth of the second fixing grooves. Accordingly, the grinding plate may be coupled to the grinding mount by placing the fixing projections in the first fixing grooves, respectively, rotating the grinding plate relative to the grinding mount to slide the fixing pins along guide the grooves until the fixing pins enter the second fixing grooves, and then pressing the grinding plate towards the grinding mount to force the coupling projections of the fixing pins through the annular packings and into the bottoms of the second fixing grooves.  
         [0013]     According to another aspect of the present invention, there is provided a grinding assembly including a grinding plate having grinding projections at the bottom thereof and at least two fixing pins protruding at the top thereof, a grinding mount having fixing grooves in the bottom surface and in which the fixing pins are received, respectively, and holding means for holding the fixing pins within the fixing grooves such that the grinding plate is coupled to the grinding plate, and fastening means for detachably securing the grinding plate to the grounding mount.  
         [0014]     The holding means of the grinding mount may comprise the annular rubber packings fixed on the walls of the grinding mount that define the sides of the second fixing grooves, respectively.  
         [0015]     The grinding mount may also have a first vacuum passage connected to the fixing grooves and/or a plurality of second vacuum passages spaced along a circle and open at the bottom surface thereof. In this case, the fastening means is a vacuum pump connected to the vacuum passage or passages.  
         [0016]     Alternatively or additionally, the fastening means may comprise at least two fastening units mounted on the sidewall of the grinding mount. Each of the fastening units includes a mechanical fastener that is capable of detachably securing the grinding plate to the grinding mount.  
         [0017]     According to still another aspect of the present invention, there is provided a method of fastening a grinding plate to a grinding mount, wherein the grinding plate is initially coupled to the grinding mount, and then is detachably secured to the grinding mount using a fastening system. The grinding plate is initially coupled to the grinding mount by inserting fixing pins of the grinding plate into fixing grooves of the grinding mount to bring a top surface of the grinding plate flush against the bottom surface of the grinding mount, and holding the fixing pins within the fixing grooves. In this respect, the fixing pins are urged to the bottom of the fixing grooves, respectively, through rubber packings each having an inner diameter smaller than that of the outer diameter of coupling projections of the fixing pins.  
         [0018]     The grinding plate may be secured to the grinding mount by forming a vacuum in the fixing grooves to thereby exert vacuum pressure on the fixing pins and/or by forming a vacuum at an interface between the bottom surface of the grinding mount and the top surface of the grinding plate. The grinding plate may also be secured to the grinding mount with mechanically fasteners. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments thereof made with reference to the attached drawings in which:  
         [0020]      FIG. 1A  is a perspective view of a prior art grinding assembly of semiconductor wafer back-grinding apparatus;  
         [0021]      FIG. 1B  is a sectional view of the prior art grinding assembly;  
         [0022]      FIG. 2  is a perspective view of a semiconductor wafer back-grinding apparatus according to the present invention;  
         [0023]      FIG. 3  is a side view of an embodiment of a grinding assembly of semiconductor wafer back-grinding apparatus according to the present invention;  
         [0024]      FIG. 4A  is a perspective of the grinding assembly according to the present invention;  
         [0025]      FIG. 4B  is a bottom view of a grinding mount of the grinding assembly according to the present invention;  
         [0026]      FIG. 4C  is a sectional view of the grinding mount taken along line  4 C- 4 C of  FIG. 4B ;  
         [0027]      FIG. 4D  is a sectional view of the grinding mount taken along line  4 D- 4 D of  FIG. 4B ;  
         [0028]      FIG. 4E  is a plane view of a grinding plate of the grinding assembly according to the present invention; and  
         [0029]      FIG. 4F  is a side view of a fastening unit of the grinding mount of the grinding assembly according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     The present invention will now be described more fully with reference to  FIGS. 2-4F .  
         [0031]     Referring first to  FIG. 2 , the semiconductor wafer back-grinding apparatus includes a wafer support  102 , a plurality of grinding bases  104  disposed on the wafer support  102  for supporting semiconductor wafers  106 , respectively, and a driving shaft  100  connected to the wafer support  102  for rotating the wafer support  102 . The apparatus further includes grinding assemblies  200  disposed above the wafer support  102 . Each grinding assembly  200  includes a grinding plate  110 , a grinding mount  130  to which the grinding plate  110  is attached, and a driving motor (not shown) connected to the grinding mount  130  by a rotational shaft  120  for rotating the grinding plate  110 . The grinding plate  110  includes a plate body and a plurality of grinding projections  118  at the periphery of the bottom of the plate body. The grinding projections  118  may contain diamond particles for grinding the back side of a wafer  106 . Also, the grinding mounts  130  are disposed above and spaced a predetermined distance from the grinding bases  104  and hence, from the wafers  106  supported on the grinding bases  104 .  
         [0032]     Referring now to  FIGS. 3 and 4 A, each grinding plate  110  also comprises at least two fixing pins  112  projecting upwardly from a flat top surface of the plate body for securely fixing the grinding plate  110  to the grinding mount  130 . To this end, each fixing pin  112  comprises a pin body and a coupling projection  114  at the top of the pin body. The coupling projections  114  may be spherical, cylindrical, or otherwise polyhedral. Also, the fixing pins  112  all lie along a circle whose center coincides with that of the top surface of the grinding plate and are spaced from each by equal distances along that circle.  
         [0033]     The grinding mount  130  has at least two first fixing grooves  136  in an otherwise flat bottom surface thereof. The first fixing grooves  136  are configured to receive the respective fixing pins  112 . In particular, the bottom of each first fixing groove  136  has a shape corresponding to that of a coupling projection  114 . In this embodiment, the walls of the grinding mount  130  defining the bottom of the first fixing grooves  136 , and the coupling projections  114  have complementary spherical surfaces. Furthermore, the walls of the grinding mount  130  defining the sides and bottom of each of the first fixing grooves  136  may be formed of rubber to prevent the coupling projections  114  from being damaged and to form a seal.  
         [0034]     The grinding mount  130  also has at least two second fixing grooves  140  and first guide grooves  138  in the bottom thereof. The first guide grooves  138  extend along arcs of a circle whose radius is the same as that of the circle along which the fixing pins are spaced from one another. Also, the first guide grooves  138  connect the second fixing grooves  140  to the first fixing grooves  136 , respectively. Each second fixing groove  140  is deeper than the first fixing groove  136  that is connected thereto. The height of the fixing pins  114  is substantially the same as the depth of the second fixing grooves  
         [0035]     The bottom of each of the second fixing grooves  140  is connected to a first vacuum passage  132  so that the second fixing groove  140  can be evacuated. A wall defining the bottom of each second fixing groove  140  has a shape corresponding to that of a coupling projection  114 . Also, the walls of the grinding mount  130  which define the sides and bottom of each of the second fixing grooves  140  may be formed of rubber to prevent the coupling projections  114  from being damaged and to facilitate the forming of a vacuum seal.  
         [0036]     Referring to  FIG. 4C , a respective annular rubber packing  135  is fixed to the wall  137  that defines the sides of each second fixing groove  140 . The rubber packing  135  has an inner diameter smaller than the diameter of the second fixing groove  140 , so as to protrude into the second fixing groove  140 , and smaller than the diameter of the coupling projection  114 . Accordingly, the rubber packing  135  will tightly contact the coupling projection  114  of the fixing pin  112 , will hold the fixing pin  112  in the second fixing groove  140  via the coupling projection  114 , and will establish a seal therewith as will be described in more detail later on.  
         [0037]     The grinding mount  130  may also have second vacuum passages  134  spaced from one another along a circle whose center coincides with that of the bottom surface of the grinding mount  130 . The second vacuum passages  134  terminate at vacuum holes  142  open at the bottom surface of the grinding mount  130 . A vacuum pump  150  is connected to the first and second vacuum passages  132  and  134  for creating a vacuum therein. On the other hand, an air injector  148 , such as a compressor, is also connected to the first and second vacuum passages  132  and  134  so as to inject air into the first and second vacuum passages  132  and  134  and thereby relieve the vacuum pressure when desired. The pressure of the first and second vacuum passages  132  and  134  is measured by a pressure sensor  146  connected to the first and second vacuum passages  132  and  134 .  
         [0038]     Referring now to  FIGS. 4B and 4D , a respective fixing ball  139  may project into each of the first guides  138  at sides thereof adjacent the second fixing grooves  140 . The fixing balls  139  function to accurately set the fixing pins  112  in the fixing grooves  140  and to prevent the fixing pins  112  from sliding out of the second fixing grooves  140  even when the vacuum produced in the fixing grooves  140  is relieved.  
         [0039]     Referring next to  FIGS. 4E and 4F , at least two fastening units  144  may be provided on a sidewall of the grinding mount  130 . Each of the fastening units  144  includes a head portion  144   a , a second guide  144   b  defining a passage, and a fixing member  144   c  integral with the head portion  144   a  such that the fixing member  144   c  can be moved along the second guide  144   b  when downward pressure is exerted on the head portion  144   a . The second guide  144   b  and the fixing member  144   c  are provided with snap projections to keep the fixing member  144   c  in place. The grinding plate  110  has third fixing grooves  116  in a sidewall thereof at positions corresponding to the passages defined by the second guides  144   b . The third fixing grooves  116  receive the fixing members  144   c , respectively, in a press- or snap-fit manner when the head portions  144   a  are pressed downwardly.  
         [0040]     A method of fastening the grinding plate  110  to the grinding mount  130  will be now be described.  
         [0041]     First, the fixing pins  112  are inserted into the first fixing grooves  136  of the grinding mount  130 , respectively. Next, the grinding plate  110  is rotated relative to the grinding mount  130  to move fixing pins  112  along the first guides  138  until the fixing pins  112  are located in the second fixing grooves  140 , respectively. At this time, the grinding plate  110  and the grinding mount  130  are pressed together to force the coupling projections  114  through the rubber packings  135  whereupon the coupling projections  114  are seated on the rubber packings  135  within the bottoms of the second fixing grooves  140 . Also, at this time, the flat top and bottom surfaces of the grinding plate  110  and the grinding mount  130  are brought into contact with each other in a horizontal plane.  
         [0042]     Thus, the fixing pins  112  are prevented from being removed from the respective second fixing grooves  140 , whereby the grinding plate  110  is coupled to the grinding mount  130 . Then, a vacuum is formed in the first and second vacuum passages  132  and  134  in the grinding mount  130 . Accordingly, the vacuum acts to maintain the fixing pins  112  within the second fixing grooves  140  via the first vacuum passages  132 , and acts to maintain the top surface of the plate body of the grinding plate  110  against the bottom surface of the grinding mount  130  via the second vacuum passages  134 . Next, the fixing members  144   c  of the respective fixing units  144  are inserted into the third fixing grooves  116  in the sidewall of the grinding plate  110 . Accordingly, the fixing members  144   c  fix the grinding plate  110  to the grinding mount  130  and ensure that the rotation of the grinding mount  130  is transferred to the grinding plate  110 .  
         [0043]     Also, once the coupling projections  114  are received within the bottoms of the second fixing grooves  140 , i.e., once the grinding plate  110  is coupled to the grinding mount  130 , the grinding plate  110  can be fastened to the grinding mount  130  in just one of those ways described above. For instance, the grinding plate  110  can be fastened to the grinding mount  130  using only a vacuum applied to the fixing pins  112  through the first vacuum passages  132  connected to the second fixing grooves  140 . Alternatively, the grinding plate  110  can be fastened to the grinding mount  130  using only a vacuum applied to the grinding plate  110  through the second vacuum passage  134 . Alternatively, the grinding plate  110  can be fastened to the grinding mount  130  by the fastening units  144 .  
         [0044]     According to the present invention, the grinding plate  110  is secured to the grinding mount  130  after the grinding plate  110  is initially coupled to the grinding mount  130  using the fixing pins  112 . Thus, the grinding plate  110  can be fastened to the grinding mount  130  quickly.  
         [0045]     Finally, although the present invention has been particularly shown and described with reference to the preferred embodiments thereof, various changes in form and details may be made thereto without departing from the true spirit and scope of the present invention as defined by the following claims.