Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1999-08-16
2001-04-17
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S287000
Reexamination Certificate
active
06217419
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of chemical-mechanical polishing, and more particularly, this invention relates to the field of chemical-mechanical polishing using a polishing table that provides a counter force against downward pressure exerted by a semiconductor wafer carrier.
BACKGROUND OF THE INVENTION
Different types of prior art rotary polishers are used in chemical-mechanical polishing of semiconductor wafers, where a thin layer of semiconductor material is planarized during the overall semiconductor manufacturing operation. The chemical-mechanical polishers typically have a heavy, circular polishing table made from a metal material or rigid ceramic material. The top surface is usually machined flat or formed smooth, and a polishing pad is glued onto the top surface. The polishing table is a predetermined diameter that is larger than the diameter of any semiconductor wafer that will be planarized in the chemical-mechanical polishing step. An abrasive slurry is fed onto the top surface of the polishing table. Typically, a semiconductor wafer carrier is positioned over the polishing table at a position for engaging the top polishing surface. The semiconductor wafer carrier holds the semiconductor wafer through an appropriate mechanism and places the semiconductor wafer against a polishing pad that is positioned on the top surface of the polishing table.
Standard prior art polishing pads in some rotary polishers usually consist of a stack with a hard layer on top of a soft under-pad. The hard pad produces a local planarization of topographical features, while the soft layer allows the stack to conform globally to the wafer shape. The use of a soft under-layer degrades the planarization ability of the top pad. However, a single layer hard pad cannot be used on a standard rotary polisher because high spots in the wafer will polish preferentially, resulting in very poor within-wafer uniformity. In order to improve global uniformity, the downward biasing force can be increased to a very high value, about 10 pounds per square inch, which flattens the semiconductor wafer and allows the pad to conform better to the semiconductor wafer. However, within-die uniformity is degraded as the downward directed force increases.
One recently developed chemical-mechanical polishing tool uses a “belt sander” approach. A single hard pad is mounted on a thin metal belt. The linear motion of the belt is used to polish the wafer. Good global uniformity can be achieved by tailoring the pressure behind the metal belt under the wafer. However, it is not always desirable to use a reciprocating movement because the technology of most chemical-mechanical polishing tools are directed to the rotary type of polishing table. An example of a reciprocating polishing table is the rectangular configured table shown and disclosed in U.S. Pat. No. 5,908,530 to Hoshizaki et al.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a chemical-mechanical polishing apparatus using a rotary polishing table that can be used in conjunction with a low down-force (less than 5 psi) and a high rotary table speed to maintain a high removal rate without sacrificing the thin wafer uniformity.
In accordance with the present invention, a chemical-mechanical polishing apparatus includes a polishing table having a top surface and an annular trench formed in the top surface and defining an annular configured polishing area in the polishing table. A drive mechanism rotates the polishing table. An annular diaphragm positioned within the annular configured polishing area. The annular diaphragm has a top surface and a bottom surface. A fluid actuated pressure mechanism is associated with the annular configured polishing area and exerts pressure upward onto the bottom surface of the annular diaphragm as the polishing table rotates for exerting an upward biasing pressure onto a polishing pad and imparting a desired counter force against any downward pressure exerted against by semiconductor wafer carrier during chemical-mechanical polishing.
The fluid actuated pressure mechanism includes a circular fluid head positioned under the polishing table in a predetermined area of the annular configured polishing area in which a semiconductor wafer will be positioned. It includes a plurality of fluid directing orifices through which fluid is directed through the fluid head upward against the bottom surface of the annular diaphragm.
In still another aspect of the present invention, an annular trench is formed within the polishing table and defined as the annular configured polishing area in the polishing table. A plurality of supports extend across the annular trench for supporting the annular diaphragm. In still another aspect of the present invention, a semiconductor wafer carrier is positioned over the polishing table at a position for engaging the top polishing surface of the annular diaphragm and holding a semiconductor wafer and placing the semiconductor wafer against a polishing pad positioned on the top surface of the polishing table. The top polishing surface of the annular diaphragm is preferably substantially coplanar with the top surface of the polishing table. A source of fluid can be connected to the fluid actuated pressure mechanism for supplying fluid under pressure. The source of fluid can comprise an air pump. The fluid actuated pressure mechanism can also include a plurality of concentric fluid carrying tubes for exerting pressure against the bottom of the annular diaphragm.
In still another aspect of the present invention, the chemical-mechanical polishing apparatus includes a polishing table having a top surface and an annular trench formed in the top surface that is dimensioned wider across the trench than the diameter of a semiconductor wafer to be polished. A drive mechanism rotates the polishing table and a biasing mechanism is positioned within the annular trench and comprises a plurality of concentric fluid carrying tubes positioned within the trench for carrying fluid under pressure.
An annular diaphragm is placed within the annular trench and engages the biasing mechanism. The annular diaphragm has a top surface for polishing a semiconductor wafer. A predetermined fluid pressure within the fluid carrying tubes exerts a desired upward biasing pressure through the biasing mechanism onto the annular diaphragm for imparting a desired counter force via a polishing pad against downward pressure exerted against a semiconductor wafer during chemical-mechanical polishing.
In still another aspect of the present invention, the chemical-mechanical polishing apparatus includes a polishing table having a top surface and a plurality of openings extending through the polishing table in an annular configuration to form an annular configured polishing area in the polishing table. Each opening is dimensioned wider than the diameter of a semiconductor wafer to be polished. A drive mechanism rotates the polishing table and an annular diaphragm is formed from a substantially rigid material positioned within the annular configured polishing area. The annular diaphragm has a top polishing surface and bottom surface.
A fluid directing mechanism is positioned under the polishing table at a predetermined area of the annular configured polishing area in which a semiconductor wafer is to be positioned for directing fluid under pressure and upward through the openings as the polishing table rotates, and onto the bottom surface of the annular diaphragm and onto the polishing pad. It thus exerts an upward biasing pressure onto the annular diaphragm and imparts a desired counter force against any downward pressure exerted against a semiconductor wafer carrier during chemical-mechanical polishing.
REFERENCES:
patent: 5643061 (1997-07-01), Jackson et al.
patent: 5664989 (1997-09-01), Nakata et al.
patent: 5816900 (1998-10-01), Nagahara et al.
patent: 5851136 (1998-12-01), Lee
patent: 5876271 (1999-03-01), Oliver
patent: 5908530 (1999-06-01), Hoshizaki et al.
patent: 5913714 (1999-06-01), V
Maury Alvaro
Rodriguez Jose
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Hail III Joseph J.
Lucent Technologies - Inc.
Nguyen Dung Van
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