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(12) United States Patent
(io) Patent No.: (45) Date of Patent:
US 7,077,880 B2 Jul. 18, 2006
(54) SURFACE MODIFIED COLLOIDAL
ABRASIVES, INCLUDING STABLE
BIMETALLIC SURFACE COATED SILICA
SOLS FOR CHEMICAL MECHANICAL
(75) Inventor: Junaid Ahmed Siddiqui, Richmond, VA (US)
(73) Assignee: DuPont Air Products Nanomaterials LLC, Tempe, AZ (US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 121 days.
(21) Appl. No.: 10/759,666
(22) Filed: Jan. 16, 2004
(65) Prior Publication Data
US 2005/0155296 Al Jul. 21, 2005
(51) Int. CI.
(52) U.S. CI 51/307; 51/308; 51/309;
(58) Field of Classification Search 51/307,
51/308,309; 106/3; 438/692,693 See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
A composition and an associated method for chemical mechanical planarization (or other polishing) are described. The composition includes a surface-modified abrasive modified with at least one stabilizer and at least one catalyst differing from the at least one stabilizer. The composition can further include a medium containing the abrasive and an oxidizing agent (e.g., hydrogen peroxide), wherein the at least one catalyst is adapted to catalyze oxidation of a substrate by the oxidizing agent. Preferably, the abrasive is alumina, titania, zirconia, germania, silica, ceria and/or mixtures thereof, the stabilizer includes B, W and/or Al, and the catalyst is Cu, Fe, Mn, Ti, W and/or V. Both the stabilizer and the catalyst are immobilized on the abrasive surface. The method includes applying the composition to a substrate to be polished, such as substrates containing W, Cu and/or dielectrics.
22 Claims, 1 Drawing Sheet
RGR Bacon "the Initiation of Polymerisation Processes by
Redox Catalysts" Quarterly Reviews, p. 287-310.
HJH Fenton "Oxidation of Tartaric Acid in Presence of Iron"
1894, 65 p. 899-910.
MCR Symons "Evidence for Formation of Free-Radical Intermediates in Some Reactions Involving Periodate" (1955) pp. 2794-2796.
Cheves Walling "Free Radicals in Solution" John Wiley & Sons (1957) pp. 564-579.
Abstract for "Comparison of Mineral and Soluble Iron Fenton's Catalysts for teh Trichloromethylene" by Teel et al., Water Research vol. 35(4) 2001, p. 977-984. "The Chemistry of Silica" by R. K. Her, Wiley Interscience (1979), p. 410-411.
Benjamin S. Lane and K. Burgess "A Cheap Catalytic, Scalable, and Environmentally Benign Method for Alkene Epoxidations" American Chem. Soc. vol. 123(12), 2001, p. 2933-2934.
"Mechanistic Aspects of Chemical mechanical Polishing of tungsten Using Ferric Ion Based Alumina Slurries" by Raghunath et al., ESP, vol. 96-22, pp. 1-15. "Electrochemical Aspects of the Chemical Mechanical Planarization of Tungsten" by Basak et al., ESP vol. 96-22, pp. 137-148.
* cited by examiner
SURFACE MODIFIED COLLOIDAL
ABRASIVES, INCLUDING STABLE
BIMETALLIC SURFACE COATED SILICA
SOLS FOR CHEMICAL MECHANICAL
BACKGROUND OF THE INVENTION
The present invention pertains to surface-modified colloidal abrasive polishing compositions and associated meth- 10 ods of using these compositions, particularly for chemical mechanical planarization (CMP, also known as chemical mechanical polishing).
CMP is now widely known to those skilled in the art and has been described in numerous patents and open literature 15 publications. Some introductory references on CMP are as follows: "Polishing Surfaces for Integrated Circuits", by B. L. Mueller and J. S. Steckenrider, Chemtech, February, 1998, pp. 38^16; and H. Landis et al., Thin Solids Films, 220 (1992), p. 1. 20
In a typical CMP process, a substrate (e.g., a wafer) is placed in contact with a rotating polishing pad attached to a platen. A CMP slurry, typically an abrasive and chemically reactive mixture, is supplied to the pad during CMP processing of the substrate. During the CMP process, the pad 25 (fixed to the platen) and substrate are rotated while a wafer carrier system or polishing head applies pressure (downward force) against the substrate. The slurry accomplishes the planarization (polishing) process by chemically and mechanically interacting with the substrate film being pla- 30 narized due to the effect of the rotational movement of the pad relative to the substrate. Polishing is continued in this manner until the desired film on the substrate is removed with the usual objective being to effectively planarize the substrate. 35
CMP processing is often employed in semiconductor manufacturing to remove excess metal at different stages. Typically, metal CMP slurries contain an abrasive, such as silica or alumina, suspended in an oxidizing, aqueous medium. 40
Surface modification of the abrasive is known. Colloidal silica, for example, has been modified with various metallic compounds as disclosed in U.S. Pat. Nos. 3,252,917, 3,620, 978 and 3,745,126; EP Patent Publication 1 000 995 Al; and also in the book entitled "The Chemistry of Silica", R. K. 45 Her, Wiley Interscience (1979), pages 410—411.
Colloidal silica has been stabilized with boric acid as disclosed in U.S. Pat. No. 2,630,410. See also co-pending U.S. patent application Ser. No. 10/245,440, filed Sep. 17, 2002, which discloses a surface-modified colloidal abrasive 50 (e.g., ceria or silica) that has been modified with boroncontaining compound(s).
In order to achieve fast tungsten or copper removal rates, oxidants and co-oxidants have been reported in the patent literature. For tungsten CMP, oxidants such as periodic acid, 55 potassium iodate, ferric nitrate, and hydrogen peroxide (H202) are commonly used. For copper CMP, H202 is a commonly used oxidant. Of all the oxidants in commercial use, H202 is low cost, and it is benign from the standpoint of product stewardship, as the byproduct is water. However 60 H202 is a poor oxidant for tungsten as it reacts very slowly, so an additive that can catalyze the reaction between tungsten and H202 during CMP is highly desirable. See, e.g., U.S. Pat. No. 5,958,288 to Mueller et al., which describes the use of soluble metal co-catalysts for activating H202 for 65 the planarization of tungsten. See also SU 1629353, which discloses a composition and method for CMP of aluminum
alloys, wherein soluble iron (iron chloride) is used to activate sodium perborate in the presence of diethyldithiophosphoric acid and ninhydrin. SU 120891 discloses a composition and method for CMP of stainless steel, wherein the composition comprises nitric acid, hydrochloric acid, water, oxalic acid, silicon dioxide powder, and acid potassium fluoride as a halogen ion source.
While the use of soluble metal co-catalysts increases the speed at which H202 reacts with tungsten, they also require CMP slurries with large concentrations of dissolved, ionic metallic components. As a result, the polished substrates can become contaminated by the adsorption of charged species from the metal co-catalysts. These species can migrate and change the electrical properties of the devices, for example at gates and contacts, and change the effective dielectric properties of dielectric layers. These changes may reduce the reliability of the integrated circuits with time. Therefore, it is desirable to expose the wafer only to high purity chemicals with very low concentrations of mobile metallic ions.
Accordingly, it is desired to provide a polishing composition that does not contain large concentrations of dissolved metal ions. It is further desired to provide a polishing composition particularly suitable for conducting metal CMP, such as copper CMP and tungsten CMP, which composition contains an additive to catalyze the reaction between metal substrate and H202, but does not contain large concentrations of dissolved metal ions.
All references cited herein are incorporated herein by reference in their entireties.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the invention provides a surface-modified abrasive modified with at least one stabilizer and at least one catalyst differing from the at least one stabilizer.
Also provided is a composition comprising a medium containing the abrasive and an oxidizing agent, wherein the at least one catalyst is adapted to catalyze oxidation of a substrate by the oxidizing agent.
Further provided is a composition comprising an abrasive having a surface on which at least one stabilizer and at least one catalyst are bonded, provided that the at least one stabilizer differs from the at least one catalyst.
Still further provided is a composition comprising an abrasive having a surface on which at least one stabilizer and at least one catalyst are bonded, wherein the abrasive is a member selected from the group consisting of alumina, titania, zirconia, germania, silica, ceria and mixtures thereof, the at least one stabilizer comprises at least one element selected from the group consisting of B, W and Al, and the at least one catalyst comprises at least one element selected from the group consisting of Cu, Fe, Mn, Ti, W and V, provided that the at least one stabilizer and the at least one catalyst are not simultaneously W.
Still further provided is a composition comprising:
an abrasive having a surface on which at least one stabilizer and at least one catalyst are bonded provided that the at least one stabilizer differs from the at least one catalyst;
an oxidizing agent; and
a medium in which the abrasive and the oxidizing agent are contained,
wherein the at least one catalyst is adapted to catalyze an oxidation reaction of the oxidizing agent with a substrate.
Still further provided is a method for polishing a surface of a substrate, said method comprising applying the composition of the invention to the surface of the substrate to