Abstract:
A cleaning cup for holding and cleaning a pad conditioner having a conditioner head, the cleaning cup includes a spray nozzle for spraying a cleaning solution on a top side of the conditioner head. The cleaning cup further includes a plurality of support pins extending upwards from a base of the cleaning cup to receive the conditioner head thereon.

Description:
BACKGROUND 
     The present invention relates generally to chemical mechanical polishing of substrates and, more particularly to a polishing pad conditioner cleaning apparatus. 
     Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. Specific structures and devices are formed by preferential etching of the layers aided by photolithography. High resolution and accurate focusing of the photolithography apparatus allows the formation of well defined micro- or nano-structures. Accurate focusing of the photolithography apparatus is difficult for non-planar surfaces. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface. 
     Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. In addition, the carrier head may rotate to provide additional motion between the substrate and polishing surface. Further, a polishing slurry, including an abrasive and at least one chemically-reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate. 
     The effectiveness of a CMP process may be measured by its polishing rate, and by the resulting finish (absence of small-scale roughness) and flatness (absence of large-scale topography) of the substrate surface. Inadequate flatness and finish can produce substrate defects. The polishing rate, finish and flatness are determined by the pad and slurry combination, the relative speed between the substrate and pad, and the force pressing the substrate against the pad. The polishing rate sets the time needed to polish a layer. Thus, it sets the maximum throughput of the polishing apparatus. 
     It is important to take appropriate steps to counteract any deteriorative factors which may either damage the substrate (such as by scratches resulting from accumulated debris in the pad) or reduce polishing speed and efficiency (such as results from glazing of the pad surface after extensive use). The problems associated with scratching the substrate surface are self-evident. The more general pad deterioration problems both decrease polishing efficiency, which increase cost, and create difficulties in maintaining consistent operation from substrate to substrate as the pad decays. 
     The glazing phenomenon is a complex combination of contamination, thermal, chemical and mechanical damage to the pad material. When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects reduce the pad&#39;s roughness and its ability to efficiently polish the substrate. 
     It is, therefore, desirable to continually condition the pad by removing trapped slurry, and unmatting or re-expanding the pad material. 
     A number of conditioning procedures and apparatus have been developed. A conventional conditioner has an arm holding a conditioner head with an abrasive disk facing the polishing pad. A bearing system rotatably supports the abrasive disk at the end of the arm. The abrasive disk rotates against the polishing pad to physically abrade the polishing pad and remove the glazing layer from the polishing pad. 
     While the abrasive disk is rotating against the polishing pad, slurry will tend to coat the conditioner head. However, when the conditioner head is not operating, e.g., between polishing operations or due to maintenance, the slurry on conditioner head will tend to dry out. As the slurry dries, it tends to form a hardened “caked” surface, and sodium hydroxide in the slurry tends to crystallize. The resulting solidified slurry particles may fall off the conditioner head onto the polishing pad. These particles may scratch the wafer during polishing. The CMP apparatus can include a cleaning cup for removing slurry deposits from a conditioner head. Unfortunately, some wafer scratching persists. 
     The slurry solidification problem has been associated generally with the abrasive disk of the conditioner head since it is the part of the conditioner head that physically contacts the polishing pad. In reality, the slurry may be splashed on other parts of the conditioner head, e.g., a top side of the conditioner head. 
     In view of the above, there is room for improvement in cleaning of the conditioner head. 
     SUMMARY 
     In general, in one aspect, the present invention features a chemical mechanical polishing apparatus comprising a pad conditioner and a cleaning cup having a base and walls extending upward from the base for holding and cleaning the conditioner head. The cleaning cup includes a spray nozzle for spraying cleaning solution onto the conditioner head. 
     Implementations of the invention may include one or more of the following features. The cleaning cup further includes a first passage for directing the cleaning solution to the spray nozzle. The cleaning cup further includes a spray nozzle support having a second passage, the spray nozzle support supporting the spray nozzle and connecting the first and second passages to direct the cleaning solution to the spray nozzle. The cleaning cup further includes a cleaning solution passage for continuously supplying the cleaning solution to the cleaning cup. The cleaning cup further includes a continuous cleaning solution passage for continuously supplying the cleaning cup with a cleaning solution. The cleaning cup further includes at least one drain to drain the cleaning solution from the cleaning cup. The cleaning solution in the cleaning cup is maintained at a substantially constant level. The cleaning solution is deionized water. The cleaning cup includes a plurality of spray nozzles. The spray nozzle sprays a cleaning solution on a top side of the conditioner head. 
     In another embodiment, the invention is a method of cleaning a chemical mechanical polishing apparatus. The method comprises placing a pad conditioner including a conditioner head in a cleaning cup; and turning on a cleaning solution dispenser to provide a cleaning solution to a top side of the conditioner head. 
     The invention provides a cleaning apparatus which can clean the entire conditioner head. The invention also provides a reliable means of cleaning an abrasive disk without undue risk of contaminating the abrasive disk. 
     Other features and advantages of the invention will be apparent from the following description of the preferred embodiments, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic exploded perspective view of a chemical mechanical polishing apparatus. 
     FIG. 2 is a top view of a polishing station wherein a pad conditioner is conditioning a polishing pad while a wafer is being polished on the polishing pad. 
     FIG. 3 is a side view of a slurry/rinse arm spraying water onto a polishing pad. 
     FIG. 4 shows a pad conditioner rotated off a polishing pad and placed in a cleaning cup while pad conditioning is not being performed. 
     FIG. 5 is a top view of a cleaning cup according to an embodiment of the present invention. 
     FIG. 6 is a cross sectional view of the cleaning cup along line  6 — 6  of FIG.  5 . 
     FIG.  7 . is a front view of a protrusion in a sidewall of the cleaning cup along line  7 — 7  of FIG.  5 . 
     FIG. 8 is a cross sectional view of a cleaning cup illustrating a conditioner head placed in the cleaning cup, according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a chemical mechanical polishing apparatus  100  includes three independently-operated polishing stations  114 , a substrate transfer station  116 , and a rotatable carousel  118  which choreographs the operation of four independently rotatable carrier heads  120 . A more detailed description of a similar polishing apparatus  100  may be found in U.S. Pat. No 5,738,574, the entire disclosure of which is incorporated herein by reference. 
     The carousel  118  has a support plate  142  with slots  144  through which drive shafts  146  extend to support the carrier heads  120 . The carrier heads  120  can independently rotate and oscillate back-and-forth in the slots  144  to produce a uniformly polished substrate surface. The carrier heads  120  are rotated by respective motors  148 , which are normally hidden behind a removable cover  150  (one quarter of which is removed in FIG. 1) of the carousel  118 . In operation, a substrate is loaded onto the transfer station  116 , from which the substrate is transferred to a carrier head  120 . The carousel  118  then transfers the substrate through a series of one or more polishing stations  114  and finally returns the polished substrate to the transfer station  116 . 
     Each polishing station  114  includes a rotatable platen  152  which supports a polishing pad  154 , a combined slurry delivery/rinse arm  155 , and a pad conditioner apparatus  156 . Each polishing station  114  also includes a cleaning cup  166  that contains a cleaning solution, such as deionized water, for rinsing or cleaning the conditioner head  160 . The platen  152 , the slurry delivery/rinse arm  155 , the conditioner rise arm apparatus  156 , and the cleaning cup  166  are mounted onto a table top  157 . 
     Each slurry/rinse arm  155  supplies slurry to an associated polishing pad  154  to facilitate the wafer polishing operation. In addition, the slurry/rinse arm can supply water to the polishing pad  154  to keep the polishing pad clean. 
     As shown in FIGS. 2 and 3, the slurry/rinse arm  155  includes a slurry nozzle  155   a  for supplying slurry to the polishing pad  154 . The slurry/rinse arm  155  also includes a plurality of water nozzles  155   b  to spray water over the polishing pad  154  to clean the polishing pad  154 . 
     Referring to FIGS. 1 and 8, each conditioner apparatus  156  includes an arm  162  that supports a conditioner head  160  over the polishing station. The arm  162  is rotatably secured to the table top  157  at a base  164 . The conditioner head  160  includes a circular bottom side  160   a , a circular top side  160   b , and side walls  160   c  generally extending from the top side  160   b  to the bottom side  160   a . The bottom side  160   a  faces the polishing pad  154  and supports or includes an abrasive conditioning disk  161 . A distal end of the arm  162  is coupled to the conditioner head  160 , and a proximal end of the arm  162  is coupled to the base  164 . The base  164  can rotate to pivot the arm  162  and thus move the abrasive disk  161  across the polishing pad surface  176 . A more complete description of a similar pad conditioner apparatus may be found in U.S. patent application Ser. No. 09/052,798, filed Mar. 31, 1998, entitled Chemical Mechanical Polishing Conditioner, by Gurusamy et al., the entire disclosure of which is incorporated herein by reference. 
     As shown in FIG. 4, between conditioning operations, the pad conditioner arm  162  pivots to move the conditioner head  160  off the polishing pad  154  and into the cleaning cup  166 . In one embodiment, the water nozzles  155   b  of the slurry/rinse arm  155  remain on when the conditioner head  160  is removed from the polishing pad  154  and inserted into the cleaning cup  166 . Alternatively, the water nozzles  155   b  of the slurry/rinse arm  155  may be deactivated when the conditioner head  160  is placed in the cleaning cup  166 . 
     Referring to FIGS. 5 and 6, the cleaning cup  166  includes a generally triangular-shaped base  168  and a sidewall  170  which extends upwardly from the perimeter of the base  168 . The sidewall  170  includes an inner wall  170   a  and an outer wall  170   b . The base  168  and the inner wall  170   a  define a triangular-shaped basin for receiving the pad conditioner head  160 . 
     The base  168  includes a lower base portion  174  portion and an upper base portion  172 . The upper base portion  172  is at a higher elevation than the lower base portion  174 . A main channel  178  separates the upper base portion  172  from the sidewall  170 . A main drain  182  may be positioned adjacent to a corner of the base  168  and connected to the main channel  178  to drain cleaning fluid from the cleaning cup  166 . Of course, the main drain  182  may be placed in other areas as well. An annular channel  176  is provided to define a border between the upper base portion  172  and the lower base portion  174 . An annular channel drain  180  is coupled to the annular channel  176 . 
     The lower base portion  174  is designed to receive the abrasive disk  161  of the conditioner head  160 . The lower base portion  174  is a circular shape to correspond to the shape of the abrasive disk  161  and the conditioner head  160 . Three support pins  184  protrude upwardly from the lower base  174 . The support pins  184  define the vertices of a triangle. The sides of the triangle defined by the support pins  184  are preferably equal in length. The support pins  184  provide a stable support to receive the abrasive disk  161  and the conditioner head  160 . The pins  184  also provide a space between the lower base  174  and the abrasive disk  161  so that a cleaning fluid may flow therebetween to clean the abrasive disk  161 . 
     A protrusion  186  extends outwardly from the sidewall  170 . As shown in FIG. 7, the protrusion  186  has two passages  188  and  190  arranged vertically for introducing cleaning solution into the cleaning cup  166 . The upper passage  188  extends from the front of the protrusion  186  and ends at the inner wall  170   a . The upper passage  188  is connected to a first cleaning solution supply (not shown) by a first tube (not shown), and continuously replenishes the cleaning solution in the cleaning cup  166 . The main drain  182  and the annular channel drain  180  are used to drain the cleaning fluid from the cleaning cup  166  so that a substantially constant level of cleaning solution  167  (see FIG. 8) is maintained in the cleaning cup  166 . 
     The lower passage  190  extends from the front of the protrusion  186 , continues under a portion  192  of the upper base  172 , and ends with a spray opening  197  on the upper base  172 . The upper passage  190  is connected to a second cleaning fluid supply (not shown) by a second tube (not shown). 
     Referring to FIGS. 5 and 8, an L-shaped spray nozzle support  194  having a passage  193  therethrough is fitted into the spray opening  197 . A spray nozzle  196  is connected an end of the spray nozzle support  194 . The spray nozzle support  194  is of sufficient length to enable the spray nozzle  196  to be positioned slightly above the top side  160   b  of the conditioner head  160  when the conditioner head  160  is located in the cleaning cup  166 . 
     As discussed, between conditioning operations, the conditioner head  160  is placed inside the cleaning cup  166 , and the abrasive disk  161  is placed on the support pins  184 . A level  198  of cleaning solution  167  in the cleaning cup  166  is maintained so that the cleaning solution  167  is slightly above the abrasive disk  161 , but is below the top side  160   b  and upper parts of the side walls  160   c  of the conditioner head  160 . The spray nozzle  196  is positioned above the conditioner head  160  to spray a cleaning solution  199  on the top side  160   b  and the upper portions of the side wall  160   c  of the conditioner head  160  to remove any slurry deposits therefrom. Specifically, slurry deposits on the side walls of the conditioner head  160  may be removed by a spray from the spray nozzle  196 , or by the flowing action of the cleaning solution as it drains off the top side  160   a  of the conditioner head  160  and flows down along the side walls  160   c . Slurry deposits on other parts of the pad conditioner  156 , e.g., a shaft  163  coupling the conditioner head  160  and the arm  162 , may also be removed by adjusting the position of the spray nozzle  196 . 
     Although only one spray nozzle has been described, additional spay nozzles may be placed in the cleaning cup  166  to more effectively clean the pad conditioner  156 . In addition, although the spray nozzle  196  has been described as positioned inside the cleaning cup  166 , the spray nozzle  196  may be positioned in other locations, e.g., outside and extending over the cleaning cup  166 . Also, although the mechanism for directing the cleaning solution has been described as a spray nozzle, other types of fluid dispensers may be used. Furthermore, a cleaning solution other than deionized water may be used to remove slurry deposits on the pad conditioner  156 . 
     The present invention has been described in terms of a preferred embodiment. The invention, however, is not limited to the embodiment depicted and described. Rather, the scope of the invention is defined by the appended claims.