Abstract:
A tool for conditioning a wafer polishing pad includes a body having a recess in the upper surface thereof. A holder has a portion extending into the recess in the body. An elastomeric member between the holder and the body acts as a gimble permitting planar contact of the tool with the pad.

Description:
TECHNICAL FIELD 
     This invention is directed to improving the performance of a tool for conditioning a semiconductor polishing pad. 
     BACKGROUND ART 
     In the production of integrated circuits the wafer on which the circuits are constructed is subjected to repetitive chemical mechanical polishing, or planarization, steps. Polishing is performed on a resilient pad in conjunction with a chemical slurry. 
     The production of quality circuits is dependent in large measure on proper conditioning, or reconditioning, of the polishing pad. Conditioning of the pad, which can be done after a wafer has been polished (ex-situ) or as the wafer is being polished (in-situ), is essentially a roughening and flattening of the pad surface. Thus, the conditioning tool is a body having an abrasive surface which is pressed against and moved across the pad. 
     U.S. Pat. No. 5,842,912, granted Dec. 1, 1998 to Holzapfel et al. for “Apparatus for Conditioning Polishing Pads Utilizing Brazed Diamond Technology” discloses a pad conditioning apparatus. U.S. Pat. No. 5,954,570, granted Sep. 27, 1999 to Yano et al. for “Conditioner for a Polishing Tool”, discloses a pad conditioning tool. 
     Both Holzapfel et al. and Yano et al. recognize that the conditioning tool should be mounted flexibly to permit the tool to have planar contact with the pad being polished. They include a ball and socket connection in the drive system above the tool. The pivot point of the ball and socket connection is a substantial distance above the abrasive surface of these tools so drag forces acting laterally across the tool surface act through a substantial moment arm tending to tilt the tool excessively and producing chatter, or vibration of the tool. The result can be uneven conditioning of the polishing pad. 
     There continues to be a need for a conditioning tool that is stable and reliable in operation. 
     SUMMARY OF THE INVENTION 
     This invention contemplates forming the conditioning tool with a body member having an abrasive peripheral lower surface and a central recess from the upper surface. A holder for the tool extends into the recess in the body member and an elastomeric member between the holder and the body member holds the latter two components together. There is clearance between the holder and the body member and the elastomeric member acts as a gimble and permits the body member to tilt with respect to the holder for planar contact with the surface of the pad being polished. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail hereinafter by reference to the accompanying drawings wherein: 
     FIG. 1 is a perspective view of a conditioning tool embodying the invention; 
     FIG. 2 is an exploded perspective view of the tool of FIG. 1; 
     FIG. 3 is a vertical sectional view of the tool taken generally as indicated by line  3 — 3  in FIG. 1; 
     FIG. 3A is an enlargement of that portion of FIG. 3 within circle  3 A in FIG. 3; and 
     FIG. 4 is a fragmentary sectional view of a modified conditioning tool. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 to  3  and  3 A, the conditioning tool there illustrated is indicated generally by reference numeral  10 . The tool comprises three principal components, namely, a body  11  having an abrasive peripheral lower surface  12  and a central recess  13  from its upper surface, a holder  14  extending down into the body recess  13 , and a elastomeric member  15  between the holder  14  and the body  11 . 
     The abrasive surface  12  may be provided on the body in a variety of ways depending upon the composition of the pad to be conditioned. One abrasive coating currently used for polishing urethane mats consists of diamond particles in a matrix of metal braze. 
     Elastomeric member  15  is preferably an O-ring having a circular cross-section and made from a chemically resistant synthetic rubber, such as Neoprene. Such rings are widely available commercially and can be obtained in selected degrees of hardness and flexibility. 
     The body  11  in the lower region of the recess  13  therein is shaped as indicated at 16 to conform to the surface configuration of the member  15  to embrace a lower portion of the member. 
     Similarly, the portion  17  of holder  14  which extends into the holder recess  13  has a concave periphery  18  shaped to conform to the surface configuration of the member  15 . 
     The lower wall region of body  11  in recess  13  could be configured like the concave region  18  of the holder  14  so the holder with member  15  in place could be snapped into place in the body. However, for ease of assembly and disassembly, it is preferred that a cylindrical retainer  19  be employed to slide into the recess and engage an upper region of the member  15 . Retainer  19  has a flange  20  at its upper end. A series of openings  21  through flange  20  permit a series of threaded bolts  22  to enter tapped bores  23  in the body  11  to secure the retainer  19  on the body  11 . 
     The resilient connection provided by member  15  between the holder  14  and the body  11 , which is sometimes referred to as a “gimble”, is superior in several respects to prior gimbles for conditioning tools. 
     In the first place, the gimble connection of this invention is down in the body  11  only a short distance above the abrasive surface  12 . Thus, the moment arm for drag forces acting on surface  12  is much lower than for the moment arm for similar forces acting on prior conditioning tools having the gimble connection well above the body of the tool. See, for example, the tools disclosed in the aforementioned Holzapfel et al. and Yano et al. patents. Furthermore, the elastomeric properties of the member  15  have a dampening effect on any tendency to chatter. The conditioning tool  10  of this invention thus has less tendency to chatter or vibrate when conditioning a pad. This results in superior surface preparation of the pad. 
     The use of the elastomeric member  15  for the gimble connection permits the performance of the conditioning tool  10  to be adjusted simply by selecting a stiffer or a softer material for the member. 
     Although, as mentioned above, elastomeric member  15  is an O-ring with a circular cross-section it could well take the form of a ring with a non-circular cross-section. Moreover, if a driving connection is desired between the holder  14  and the body  11  then the portion  17  of the holder and the recess  13  may have complementary non-circular configurations. In that case the elastomeric member  15  would possess a similar configuration. 
     If a stiffer or softer gimble is desired it is possible to equip the tool with two or more members  15  as shown in FIG.  4 . The portion  17  of the holder  14  and the retainer  19  are simply configured to accommodate the additional member or members.