Abrading – Work holder – Work rotating
Reexamination Certificate
2000-03-30
2001-07-24
Banks, Derris H. (Department: 3723)
Abrading
Work holder
Work rotating
C451S288000
Reexamination Certificate
active
06264540
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a disposable bladder carrier assembly for retaining workpieces such as semiconductor wafers. More particularly, the present invention relates to a one piece disposable bladder carrier assembly where a rubber bladder is molded directly to a retaining ring having a rigid ring surrounded by a bonded wear resistant plastic such as polyether ethyl ketone (PEEK) or ultra-high molecular weight polyethylene (UHMW) polyethylene. The rubber bladder is permanently bonded to the rigid ring and may also be bonded to the wear resistant plastic depending upon the particular embodiment of the bladder carrier assembly.
BACKGROUND OF THE INVENTION
Presently known chemical mechanical polishing machines typically employ either a single carrier or a plurality of carriers, each configured to hold a single semiconductor wafer firmly against a polishing surface, for example the upper surface of a rotating polishing pad. As a result of the relative motion between the semiconductor wafer surface to be polished and the polishing pad, coupled with the downward pressure applied by the wafer carrier to press the wafer against the polishing pad, even very small deviations in the uniformity of the pressure applied to the semiconductor wafer across the wafer surface can result in imperfections in the planarization process. In order to maintain a uniform pressure to the semiconductor wafer, current carriers often comprise a flexible membrane, or bladder, that covers a downward opening on the underside of a carrier thereby creating a space between the carrier and the bladder. An idealized bladder system expands or translates primarily in the axis of the wafer. When a pressurized fluid is applied to the space, the bladder applies a uniform downward pressure across the entire upper surface of a wafer that is being polished. One example of such a carrier can be found in U.S. Pat. No. 5,449,316 issued to Strasbaugh.
Although current carriers employing a bladder enable uniformity, carrier to carrier identicalness is a problem. Further, current carrier designs employing a bladder have a high cost of ownership due to several factors relating to lifetime of the carrier and replacement costs of the carrier such as downtime, wear on the retaining ring, ring delamination, part fatigue, assembly reproducibility and difficulty in assembling the carriers. In addition, current carriers employ adhesives and/or compressive joints which can fail as a result of too much pressure and vacuum cycling in a wet corrosive environment.
Accordingly, there is a need for a reliable bladder carrier that is cost efficient and time efficient. There is also a need for a method for making such a bladder carrier that further reduces cost of ownership.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention relates to a one-piece bladder carrier assembly having a bladder that is permanently bonded to a retaining ring structure for retaining workpieces during processing. The bladder carrier assembly includes a rigid ring, preferably comprised of steel, a wear resistant material, such as ultra-high molecular weight (UHMW polyethylene, PEEK, polyetherketone, polyphenylene sulfide, polybutylene terthalate, and homopolymer acetal, which is formed around the rigid ring, and a bladder that is permanently bonded to the steel after or when it is cast. In another aspect of the invention, the bladder may also be permanently bonded to the wear resistant material. In addition, a cavity may be formed either within the wear resistant material, or within both the wear resistant material and the rigid ring to create a pressure wave relief space.
In general, in another aspect, the invention relates to a method for making a one-piece bladder carrier assembly. A rigid ring having bore holes is made and then mounted on a hardened steel plate. This assembly is then placed in a mold and a wear resistant material, such as UHMW polyethylene or PEEK, is formed around, and bonded to, the rigid ring by employing increased temperature and pressure. A bladder material such as EPDM rubber is molded concurrently with the ring structure such that the bladder is permanently bonded to either the rigid ring, or both the wear resistant material and the rigid ring. In another aspect of the invention, the bladder may be molded to the ring structure in a second step subsequent to the formation of the ring structure.
A main advantage of the invention is a reduced cost of ownership due to an increase in the lifetime of the carrier and a decrease in replacement costs. A further cost ownership advantage is the time and simplicity of part change procedures in a simple, one piece bolt up type assembly.
REFERENCES:
patent: 5449316 (1995-09-01), Strasbaugh
patent: 6019670 (2000-02-01), Cheng et al.
patent: 6019671 (2000-02-01), Shendon
patent: 6077155 (2000-06-01), Hayakawa et al.
Banks Derris H.
Snell & Wilmer L.L.P.
SpeedFam-IPEC Corporation
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