Abrading – Machine – Rotary tool
Reexamination Certificate
1999-08-03
2001-09-04
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S056000
Reexamination Certificate
active
06283840
ABSTRACT:
BACKGROUND
The invention relates chemical mechanical polishing of substrates, and more particularly to dispensing slurry onto a polishing pad and cleaning the polishing pad.
Chemical mechanical polishing (CMP) is a process by which a substrate surface is planarized to a uniform level. In a conventional CMP apparatus, substrate is mounted on a rotatable carrier head and pressed against a rotating polishing pad. An abrasive chemical solution (slurry) is applied onto the polishing pad to aid in the polishing of the substrate to achieve a desired surface finish. Over time, the polishing process glazes the polishing pad and creates irregularities in the polishing pad surface that can adversely affect the substrate surface finish. The polishing pad surface is typically “conditioned” by scouring the polishing pad surface with an abrasive device known as a conditioning disk to deglaze and roughen the polishing pad surface. Periodically conditioning the pad maintains the pad surface at a consistent state of roughness to achieve consistent polishing uniformity.
One problem encountered in CMP is the generation of contaminants on the polishing pad surface during the polishing and conditioning procedures. These contaminants have a material adverse affect on the polishing process. For example, contaminants include (but are not limited to) abraded polishing pad material, dried slurry particles, conditioning disk material and airborne contaminants. Adverse material effects include (but are not limited to) scratching of the substrate and embedding of the particles in the polishing pad or substrate. It would be advantageous if the polishing apparatus cleaned the polishing pad to provide a substantially contaminant-free polishing pad.
Another problem in CMP is that slurry is an expensive consumable. A CMP system may use more than two hundred milliliters of slurry per minute. In general, the substrate takes two to three minutes to polish. Thus, a CMP system can use up to a sixth of a gallon of slurry per substrate. The per substrate cost of CMP could be reduced considerably by reducing the amount of slurry used. In addition, where excessive slurry is applied, the substrate can hydroplane over the surface of the polishing pad, thereby reducing the polishing rate. It would be advantageous if the CMP apparatus that reduced slurry consumption in the polishing process.
SUMMARY
In one aspect, the invention is directed to an apparatus for use in a chemical mechanical polishing system. The apparatus has a housing positionable over a polishing pad and at least one nozzle covered by the housing to spray a cleaning fluid against the polishing pad.
Implementations of the invention may include the following. The cleaning fluid may be deionized water, and may be sprayed by the nozzle under hydraulic pressure. The housing may extends toward the center of the polishing pad, and may be configured to be raised and lowered over a region of the polishing pad. A retainer may be joined to a lower surface of the housing, and may contact a surface of the polishing pad, e.g., at a pressure less than about 5 psi. A first feed line may supply the cleaning fluid to the assembly, a second feed line may supply a solution of deionized water and an agent selected from the group consisting of a corrosion inhibitor, a cleaner, an oxidizer, a pH adjustor, a dilution fluid, and a surface wetting agent, and a third feed line may supply an abrasive solution.
In another aspect, the invention is directed to a method of cleaning the surface of a polishing pad in a chemical mechanical polishing system. A cleaning fluid is directed from a cleaning assembly against a polishing pad that has residual contaminants, and the cleaning fluid is substantially contained within a housing of the cleaning assembly.
Implementations of the invention may include the following features. The cleaning fluid may be deionized water, and droplets of the cleaning fluid may be produced by subjecting the deionized water to a hydraulic pressure, e.g., of less than about 60 psi, such as less than about 10 psi.
In another aspect, the invention is directed to an apparatus for distributing slurry onto a polishing surface. The apparatus has a retainer having a lower surface in close proximity to the polishing surface and enclosing a region, and an outlet to distribute slurry to the enclosed region to form a reservoir of slurry in the enclosed region. The slurry is distributed to a region not enclosed by the retainer by traveling between the polishing surface and the lower surface of the retainer.
In another aspect, the invention is directed to a method of preparing the surface of a polishing pad in a chemical mechanical polishing system for polishing a substrate. In the method, a cleaning fluid impinges against the polishing pad having at least one of residual polishing slurry, contaminants and fluid. the cleaning fluid, residual polishing slurry, contaminants and fluid are substantially contained by means of a housing. The housing is lifted to expel at least a portion of the residual polishing slurry, contaminants and fluid from the polishing pad. A polishing slurry is applied to the polishing pad, and the polishing slurry is spread over the polishing pad with a lower surface of the housing.
The present invention advantageously cleans the polishing pad to provide a substantially contaminant-free polishing pad. The invention also can apply a uniform layer of polishing slurry to the polishing pad to provide improved polishing and planarization of the substrate while minimizing/optimizing the amount of slurry used.
Other features and advantages will become apparent from the following description, including the drawings and the claims.
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Applied Materials Inc.
Fish & Richardson
Hail III Joseph J.
Thomas David B.
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