Method of polishing a tungsten-containing substrate

Abstract

The invention provides a chemical-mechanical polishing composition particularly useful in polishing tungsten-containing substrates. The composition comprises a tungsten etchant, an inhibitor of tungsten etching, and water, wherein the inhibitor of tungsten polishing is a polymer, copolymer, or polymer blend comprising at least one repeating group comprising at least one nitrogen-containing heterocyclic ring or a tertiary or quaternary nitrogen atom.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS [0001] This patent application is a continuation of copending U.S. patent application Ser. No. 11 / 670,137, filed Feb. 01, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 10 / 869,397, filed Jun. 16, 2004, now issued as U.S. Pat. No. 7,247,567.FIELD OF THE INVENTION [0002] This invention pertains to the chemical-mechanical polishing of substrates comprising tungsten. The invention further provides a polishing composition comprising ferric ion, a polymer, silica, malonic acid, and water. BACKGROUND OF THE INVENTION [0003] Integrated circuits are made up of millions of active devices formed in or on a substrate, such as a silicon wafer. The active devices are chemically and physically connected into a substrate and are interconnected through the use of multilevel interconnects to form functional circuits. Typical multilevel interconnects comprise a first metal layer, an interlevel dielectric layer, and sometimes a t...

AI Technical Summary

Benefits of technology

[0007] The invention provides a method of chemically-mechanically polishing a substrate comprising tungsten comprising (i) contacting a substrate comprising tungsten with a polishing pad and a chemical-mechanical polishing composition comprising (a) a tungsten etchant, (b) an inhibitor of tungsten etching, where the inhibitor of tungsten polishing is present in an amount of about 1 ppm to about 1000 ppm, and (c) water, (ii) moving the polishing pad relative to the substrate with the polishing composition therebetween, and (iii) abrading at least a portion of the substrate to polish the substrate. The inhibitor of tungsten etching is a polymer, copolymer, or polymer blend comprising at least one repeating group comprising at least one nitrogen-containing heterocyclic ring or a tertiary or quaternary nitrogen atom. The invention further provides a polishing composition comprising (a) ferric ion, (b) an inhibitor of tungsten etching, where the inhibitor of tungsten etching is present in an amount of about I ppm to about 1000 ppm, (c) silica, (d) malonic acid, and (e) water, wherein the inhibitor of tungsten etching is as recited above.

Problems solved by technology

After exposure of the oxide layer and before completion of the polishing process, tungsten in the trenches undesirably can be eroded by a combination of static etching and by mechanical action of the abrasives, leading to dishing and erosion.

Dishing may compromise circuit integrity and leads to surface non-planarity, which may complicate deposition of metal layers on subsequent levels of the device.

However, such inhibitors are not always effective at preventing erosion of tungsten within trenches.

Additionally, use of high levels of such inhibitors of tungsten etching can reduce the polishing rates of substrates comprising tungsten layers to unacceptably low levels.