Abstract:
A platen structure of a polishing apparatus for semiconductor wafer and a method for exchanging a polishing pad affixed to the same are provided in which the polishing pad supported by the platen is exchanged with convenience within a short time. The platen structure of the polishing apparatus in which the polishing pad attached to the platen of the polishing apparatus comprises a pad plate to which the polishing pad for polishing a wafer is attached, and a platen body combined with the pad plate and having at least one vacuum hole formed thereto to provide a vacuum passage.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Korean Patent Application No. 10-2004-0093369, filed Nov. 16, 2004, the disclosure of which is hereby incorporated herein by reference in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The present invention relates to a polishing apparatus for a semiconductor wafer and, more particularly, to a platen structure of the polishing apparatus, and to a method for exchanging a polishing pad affixed to the same. This can allow the polishing pad for planarizing a metallic layer formed on the wafer surface to be exchanged for a new pad without interrupting the operation of the equipment in the manufacturing process of semiconductor devices.  
         [0004]     2. Discussion of Related Art  
         [0005]     Generally, semiconductor devices have a step whose height is increased with high densification, scale-down in line width, and multi layered metallization. In order to planarize this step, various planarizing methods such as spin on glass (SOG), etchback, reflow and the like have been developed and employed.  
         [0006]     As for such planarizing process for wafers, there are two methods comprising a mechanical polishing method and a chemical polishing method. The mechanical polishing has a drawback of forming a strained layer in the wafer during polishing. Although such strained layer is not formed, the chemical polishing also has a drawback in that it is difficult to form a planarized shape on the wafer. Thus, obtaining shape precision is not easy to accomplish. A planarizing process has been developed combining mechanical and chemical polishing, i.e., a chemical mechanical polishing (CMP) technology. The CMP process is implemented by rotating a polishing table on which a polishing pad is attached. This is done while pressing a polishing head being rotated and vibrated at a time, with a certain pressure exerted towards the polishing table. The polishing head is attached by means of surface tension or vacuum. Then, the wafer surface contacts the polishing pad using the weight of the polishing head itself and pressure applied from an exterior source. A slurry of polishing solution flows through a fine gap between the contact surfaces to facilitate a mechanical removal operation by grinding particles contained in the slurry and surface protrusions of the polishing pad, and a chemical removal operation by chemical components of the slurry.  
         [0007]     Such a polishing apparatus is disclosed in U.S. Pat. No. 6,520,895 B2. The polishing apparatus of U.S. Pat. No. 6,520,895 B2 includes a wafer chuck for supporting a wafer while directing the wafer surface to be polished upwards, a polishing pad for polishing the surface to be polished, and a polishing head for supporting the polishing pad while directing the grinding surface of the pad downwards. In this polishing apparatus, a vacuum suction device is provided at a lower portion of the polishing head so as to detachably and fixedly support the polishing pad such that the grinding surface of the pad faces downwards, by which the vacuum suction device and the polishing pad supported by the polishing head can be automatically exchanged.  
         [0008]     The conventional polishing apparatus of  FIGS. 1, 2   a  and  2   b , respectively, includes a polishing head  10  for vacuuming a wafer  12 , a polishing pad  16  mounted below the polishing head  10  so as to polish the wafer  12 , a platen  20  for fixing the polishing pad  16 , a pad conditioner  14  mounted spaced in horizontal direction located apart at a certain distance from the polishing head  10  so as to maintain the surface state of the polishing pad  16  constant, a cleaning cup  18  for cleaning the pad conditioner  14 , and a head cup load unit (HCLU)  22  for loading the wafer  12  to the polishing head  10 .  
         [0009]     The wafer  12  loaded from the HCLU  22  is moved by vacuum onto the polishing head  10 , and the polishing head  10  retaining the wafer  12  moves the wafer  12  toward each platen  20 . After the movement, the polishing head  10  exerts a pressure toward the platen, thus to the wafer positioned between the polishing pad  16  of the platen  20  and the polishing head  10 . Then, the polishing pad  16  and the polishing head  10  are rotated to polish a portion of the wafer. Herein, at a certain cycle during the continuous polishing of the wafer, a controller (not shown) controls the polishing head  10  to be positioned spaced apart from the polishing pad  16  and operates the driving of the CMP equipment including interrupting the supply of the slurry through the nozzle.  
         [0010]     Further, the pad conditioner  14  plays an important role in the polishing operation, as follows:  
         [0011]     First, the pad conditioner  14  sweeps the polishing pad so that the slurry of polishing solution is distributed uniformly around the whole surface of the wafer, which prevents the wafer from being locally polished. Second, if the polishing pad  16  contacts and continuously polishes the wafer  12 , a groove of the polishing pad  16  is worn out due to friction therebetween and thereby degrading the performance of the polishing. The pad conditioner  14  exerts at its diamond disc a force against the polishing pad  16  so that the roughness of the polishing pad can be maintained at a certain level through the sweeping and rotation of the pad conditioner, which prevents the degradation in performance of polishing.  
         [0012]     The operation of exchanging the polishing pad  16  supported by the platen  20  will now be described in the conventional wafer polishing apparatus, such as in the above apparatus. The wafer polishing apparatus including platens  20  is interrupted in its operation when all of the platens  20  are idled. Upon the exchange of the polishing pad  16 , the polishing head  10  is moved or detached to provide a space for the pad exchange. Then, the used polishing pad  16  is removed and a new polishing pad  16  is attached to the platen  20 . Finally, the polishing head  10  that has been moved or detached for securing the exchange space is returned to its original position.  
         [0013]     However, the platen structure of the conventional wafer polishing apparatus constructed as above has a problem in that the exchange of the polishing pad is inconvenient and time-consumable to implement. This is because the exchange of the polishing pad supported by the platen is conducted by interrupting the operation of equipment, moving or detaching the polishing head for securing a space for exchange, and finally exchanging the polishing pad.  
       SUMMARY  
       [0014]     Therefore, the present invention is directed to provide a platen structure of a polishing apparatus for semiconductor wafer and a method for exchanging a polishing pad affixed to the same in which the polishing pad supported by the platen is exchanged with convenience within a short time.  
         [0015]     In accordance with an exemplary embodiment of the present invention, there is provided a platen structure of a polishing apparatus. The platen structure comprises a pad plate to which a polishing pad for polishing a wafer is attached and a platen body combined with the pad plate and defining at least one vacuum hole formed therein for providing a vacuum passage. The vacuum hole preferably forms a vacuum for moving the pad plate against the platen body.  
         [0016]     The platen structure can further comprises at least one pusher seated to an edge portion of the platen body, and at least one pusher insert hole formed in the platen body into which the pusher is inserted. The pusher preferably moves up the pad plate upon the exchange of the polishing pad, so as to separate the pad plate from the platen body. The pusher is preferably a T-type pusher.  
         [0017]     The pad plate and the platen body are preferably located opposite to each other, and are combined with each other. Preferably, the pad plate and the polishing pad can be formed in one piece. The pad plate and the polishing pad can also preferably be detachable from each other. The pad plate and the platen body preferably have uneven shapes, respectively.  
         [0018]     A method for exchanging a polishing pad affixed to a platen of a polishing apparatus for semiconductor wafer can also be provided. The polishing apparatus can include a pad plate to which a polishing pad for polishing a wafer is attached, a platen body combined with the pad plate and having at least one vacuum hole formed thereto to provide a vacuum passage, at least one pusher seated to an edge portion of the platen body, and at least one pusher insert hole formed to the platen body and into which the pusher is inserted. The method can comprise the steps of providing a vacuum through the vacuum hole when the platen is in an idling state, without interrupting operation of the polishing apparatus, separating the pad plate from the platen body by pushing up the pad plate through raising the pusher, placing the pad plate having a new polishing pad attached thereto onto the pusher; lowering the pusher through the pusher insert hole such that a recessed portion of the pad plate is correspondingly engaged with a protruding portion of the platen body, and moving the pad plate against the platen body by maintaining the vacuum through the vacuum hole. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which:  
         [0020]      FIG. 1  is a plan view of a construction of a conventional wafer polishing apparatus;  
         [0021]      FIG. 2A  is a view illustrating a conventional polishing apparatus for a semiconductor wafer wherein a pad conditioner of the apparatus is mounted to a polishing pad;  
         [0022]      FIG. 2B  is a view illustrating a conventional polishing apparatus for semiconductor wafer wherein a pad conditioner of the apparatus is mounted on a cleaning cup;  
         [0023]      FIG. 3  is a view illustrating a wafer polishing apparatus according to an embodiment of the present invention;  
         [0024]      FIG. 4  is a view illustrating a platen  108  of  FIG. 3  in a disassembled state; and  
         [0025]      FIG. 5  is a view illustrating a platen  108  of  FIG. 3  in an assembled state. 
     
    
     DETAILED DESCRIPTION  
       [0026]     The present invention will now be described more fully hereinafter with reference to the accompanying drawings. In describing the present invention, if considered that the details on the related known function or construction may unnecessarily render the scope of the present invention ambiguous, the detailed description thereof will be omitted.  
         [0027]     Referring to  FIG. 3 , the polishing apparatus includes a polishing head  100  for vacuum sucking a wafer  102 , a polishing pad  106  mounted below the polishing head  100  so as to polish the wafer  102 , a platen  108  for fixing the polishing pad  106 , a pad conditioner  104  mounted spaced in horizontal direction apart a certain distance from the polishing head  100  so as to maintain the surface state of the polishing pad  106  constant, and a cleaning cup  200  for cleaning the pad conditioner  104 .  
         [0028]     Referring to  FIGS. 3-5 , the platen  108  includes the polishing pad  106  for polishing the wafer  102 , a pad plate  202  whose lower surface is formed with an uneven shape and supports the polishing pad  106 , a platen body  204  whose upper surface is formed with an uneven shape and which is engaged with the pad plate  202 , a pusher insert hole  208  formed in the recessed portion at an edge portion of the platen body  204 , a plurality of T-type pushers  210  inserted into the pusher insert hole  208  and seated in the recessed portion of the edge portion of the platen body  204 , a plurality of pusher insert holes  208  formed in the recessed portion of the platen body  204  and through which the T-type pushers  210  are inserted, and a plurality of vacuum holes  206  formed in the protruded portion of the platen body  204  to provide a vacuum passage.  
         [0029]     The platen  108  of the present invention is configured such that the recessed portion of the pad plate  202  is engaged with the protruded portion of the platen body  204 .  
         [0030]     The operation of embodiments of the present invention will now be described in detail with reference to  FIGS. 3-5 .  
         [0031]     In polishing operation of the wafer polishing apparatus to which the embodiments of the present invention are adapted, the wafer  102  is attached by vacuum to the polishing head  100 , and the polishing head  100  holding the wafer  102  moves the wafer  102  to each platen  108 . The polishing head  100  is moved toward the platen  108  and exerts a pressure thereto to thus press the wafer  102  placed between the polishing pad  106  on the platen  108  and the polishing head  100 . The polishing pad  106  and the polishing head  100  are respectively rotated to polish a portion of the wafer. At this time, in order to assist wafer polishing, a slurry of polishing solution is supplied onto the polishing pad  106 . To distribute the slurry uniformly around the whole surface of the wafer  102 , a grinding disc attached to a pad conditioner  104  is moved on the polishing pad  106 . Herein, the pad conditioner  104  is mounted spaced apart at a predetermined distance from the polishing head  100 . When the pad conditioner is not operated, it may be positioned in the cleaning cup  200  to conduct a cleaning step. However, when the pad conditioner  104  is operated, the pad conditioner  104  is moved upwards within the cleaning cup  200 , and is moved horizontally to press the polishing pad  106 , thereby maintaining the surface state of the polishing pad  106  at a constant level.  
         [0032]     After conditioning the wafer as describe herein, the pad conditioner  104  is moved upwards from the polishing pad  106 , is moved horizontally to a position on the cleaning cup  200 , and is lowered into the cleaning cup  200 . A pressure for conditioning the polishing pad  106  can be, for example, about 5.5 psi, and a pressure for seating in the cleaning cup  200  can, for example, about 4.5 psi.  
         [0033]     An operation of exchanging the polishing pad  106  supported by the platen  108  will now be described in the wafer polishing apparatus of the present invention described above.  
         [0034]     The wafer polishing apparatus having a plurality of platens  108  introduces a vacuum through the plurality of vacuum holes  206  when all of the platens are in an idling state, without interrupting the operation of the apparatus, so that the pad plate  202  is not moved against the platen body  204  by the vacuum. Then, a user moves a plurality of pushers  210  upwards to raise the pad plate  202 , separating the same from the platen body  204 . Herein, the pad plate  202  has attached thereon the polishing pad  106 . Thus, when the pad plate  202  is separated from the platen body  204 , the polishing pad  106  is also separated therefrom. Then, the user places the pad plate  202  on the T-type pusher  210 . The T-type pusher is attached on the new polishing pad  106 . The T-type pusher  210  is then lowered through the pusher insert hole  208  so that the recessed portion of the pad plate  202  is engaged with the protruded portion of the platen body  204 . In this state, if a vacuum is maintained through the plurality of vacuum holes  206  formed in the platen body  204 , the pad plate  202  is moved against the platen body  204 .  
         [0035]     The pad plate  202  can be formed integrally with or separately from the polishing pad  106 . In separated form, the polishing pad is separately attached to the pad plate.  
         [0036]     The pad plate  202  and the platen body  204  are described herein with uneven shapes which are opposite to each other so as not to slip relative to each other upon polishing the wafer  102 . These uneven shapes can include all of structures correspondingly engaged with each other so as not to slip relative to each other.  
         [0037]     As described before, the polishing apparatus having a plurality of platens is constructed so that the polishing pad is attached to the pad plate and preferably can be separated from the platen body. This allows the pad plate to be detached from and attached to the platen body even in a narrow space between the platen and the polishing head. Thus, when the platens are idling, the polishing pad can be exchanged without interrupting the operation of the apparatus, so that the polishing pad can be readily and conveniently changed within a short time.  
         [0038]     The invention has been described using preferred exemplary embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.