Abrasive tool making process – material – or composition – With inorganic material – Clay – silica – or silicate
Reexamination Certificate
2002-03-05
2004-01-27
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
Clay, silica, or silicate
C106S003000, C438S692000, C438S693000, C216S089000, C216S099000
Reexamination Certificate
active
06682575
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to CMP polishing compositions comprising silica abrasive, as well as methods of polishing substrates with such polishing compositions.
BACKGROUND OF THE INVENTION
Compositions and methods for planarizing or polishing the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries) typically contain an abrasive material in an aqueous solution and are applied to a surface by contacting the surface with a polishing pad saturated with the polishing composition. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. U.S. Pat. No. 5,527,423, for example, describes a method for chemically-mechanically polishing a metal layer by contacting the surface with a polishing slurry comprising high purity fine metal oxide particles in an aqueous medium. The polishing slurry is typically used in conjunction with a polishing pad (e.g., polishing cloth or disk). Suitable polishing pads are described in U.S. Pat. Nos. 6,062,968, 6,117,000, and 6,126,532 which disclose the use of sintered polyurethane polishing pads having an open-celled porous network and U.S. Pat. No. 5,489,233 which discloses the use of solid polishing pads having a surface texture or pattern. Alternatively, the abrasive material may be incorporated into the polishing pad. U.S. Pat. No. 5,958,794 discloses a fixed abrasive polishing pad.
Conventional polishing systems and polishing methods typically are not entirely satisfactory at planarizing semiconductor wafers. In particular, polishing compositions and polishing pads can have less than desirable polishing rates or polishing selectivities, and their use in chemically-mechanically polishing semiconductor surfaces can result in poor surface quality. Because the performance of a semiconductor wafer is directly associated with the planarity of its surface, it is crucial to use a polishing composition and method that results in a high polishing efficiency, selectivity, uniformity, and removal rate and leaves a high quality polish with minimal surface defects.
The difficulty in creating an effective polishing system for semiconductor wafers stems from the complexity of the semiconductor wafer. Semiconductor wafers are typically composed of a substrate, on which a plurality of transistors has been formed. Integrated circuits are chemically and physically connected into a substrate by patterning regions in the substrate and layers on the substrate. To produce an operable semiconductor wafer and to maximize the yield, performance, and reliability of the wafer, it is desirable to polish select surfaces of the wafer without adversely affecting underlying structures or topography. In fact, various problems in semiconductor fabrication can occur if the process steps are not performed on wafer surfaces that are adequately planarized.
The use of alcohols in polishing compositions is well known in the art. For example, U.S. Pat. Nos. 5,391,258 and 5,476,606 disclose a polishing composition comprising an abrasive and an anion containing two acid groups (e.g., hydroxyl groups), which purportedly controls the rate of removal of silica. U.S. Pat. No. 5,614,444 discloses polishing compositions comprising polishing additives having a polar component (e.g., an alcohol) and a non-polar component (e.g., an alkyl group). The polishing additive is used to suppress the removal rate of a dielectric material. U.S. Pat. No. 5,733,819 discloses a polishing composition comprising silicon nitride abrasive, water, acid, and optionally a water-soluble alcohol additive (e.g., ethanol, propanol, ethylene glycol). U.S. Pat. No. 5,738,800 discloses an aqueous polishing composition comprising abrasive, a surfactant, and a complexing agent comprising two functional groups (e.g., hydroxyl groups), which purportedly complexes silica and silicon nitride layers. U.S. Pat. No. 5,770,103 discloses a polishing composition comprising mono-, di-, or tri-substituted phenol compounds, which purportedly increase the removal rates of titanium substrate layers. U.S. Pat. No. 5,895,509 discloses a polishing composition comprising an abrasive, isopropyl alcohol, and water. U.S. patent application Ser. No. 2001/0013506 discloses a polishing composition comprising abrasive particles, an oxidizer, a pH of about 5 to about 11, and optionally an organic diluent (e.g., methanol, ethanol, ethylene glycol, or glycerol). EP 1 150 341 A1 discloses the use of alcohols as dissolution promoters in polishing compositions comprising a film-forming agent. JP 11116942 discloses a polishing composition comprising silica, water, a water-soluble polymeric compound, a base, and a compound having 1-10 alcoholic hydroxyl groups. JP 2000230169 discloses an aqueous polishing composition comprising silica, a pH buffer, and a water-soluble polishing accelerator (e.g., an alcohol), which purportedly improves polishing rates. WO 98/48453 discloses a polishing composition comprising spherical silica, an amine hydroxide, and an alkaline liquid carrier comprising up to about 9% alcohol, which purportedly increases polishing rates. WO 01/84613 discloses the use of a fixed abrasive article and an aqueous polishing composition comprising a polar component (e.g., methanol, ethanol, etc.), which purportedly reduces the surface tension of the polishing composition and provides better wetting of the surface of hydrophobic substrates.
There remains a need, however, for alternative polishing compositions, which exhibit satisfactory polishing characteristics, such as good removal rates and low surface defects. The invention seeks to provide such a polishing composition and method. These and other advantages of the invention will be apparent from the description of the invention provided herein.
BRIEF SUMMARY OF THE INVENTION
The invention provides a polishing composition comprising (a) a silica abrasive, (b) methanol, and (c) a liquid carrier, wherein the polishing composition has a pH of about 1 to about 6 and the interaction between the silica abrasive and the methanol provides colloidal stability to the polishing composition. The invention also provides a method for polishing a substrate comprising a silicon-based dielectric layer using the polishing composition. The invention further provides a method of stabilizing silica abrasive by contacting the abrasive with methanol.
DETAILED DESCRIPTION OF THE INVENTION
The invention is directed to a polishing composition comprising silica abrasive, methanol, and a liquid carrier. The polishing composition has a pH of about 1 to about 6. The interaction between the silica abrasive and the methanol provides colloidal stability to the polishing composition.
The silica abrasive typically is selected from the group consisting of fumed silica, colloidal silica, silica-coated abrasive particles, silica-containing co-formed particles (e.g., aluminosilicates), and combinations thereof. Silica-coated abrasive particles can include silica-coated alumina or silica-coated polymer particles. The silica-containing co-formed particles typically contain about 10 wt. % or more silicon. Any suitable amount of silica can be present in the polishing composition. The polishing composition typically comprises silica abrasive in an amount of about 0.1 wt. % or more (e.g., about 0.5 wt. % or more). The polishing composition typically also comprises silica abrasive in an amount of about 5 wt. % or less (e.g., about 2 wt. % or less or about 1 wt. % or less).
The interaction of the silica abrasive with the methanol under acidic conditions results in a polishing composition that is colloidally stable. Colloidal stability refers to the maintenance of the suspension of abrasive particles over time. In the context of this invention, the polishing composition is considered colloidally stable if, when 100 ml of the polishing composition placed in a 100 ml graduated cylinder and allowed to stand unagitated for a time of 2 hours, the difference between the concentration of particles in the bottom 50 ml of the gr
Cabot Microelectronics Corporation
Marcheschi Michael
LandOfFree
Methanol-containing silica-based CMP compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methanol-containing silica-based CMP compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methanol-containing silica-based CMP compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3220817