Composition for selectively polishing silicon nitride layer and polishing method employing it

• US 7,217,989 B2
• Filed: 10/18/2005
• Issued: 05/15/2007
• Est. Priority Date: 10/19/2004
• Status: Active Grant

• Current Assignee: Fujimi Incorporated
• Original Assignee: Fujimi Incorporated
• Inventors: Hori, Tetsuji, Ito, Takashi, Hiramitsu, Ai
• Primary Examiner(s): Nhu; David
• Application Number:
  US11/251,880
• Publication Number:
  US 20060084270A1
• Time in Patent Office: 574 Days
• Field of Search: 257/411, 257/410, 257/639, 257/640, 257/646, 257/649
• US Class Current: 257/639
• CPC Class Codes: C09G 1/02 containing abrasives or grinding agents abrasives as such C09K3/14; polishing of semi-conductors H01L
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step

Abstract

To provide a polishing composition whereby the stock removal rate of a silicon nitride layer is higher than the stock removal rate of a silicon oxide layer, there is substantially no adverse effect against polishing planarization, and a sufficient stock removal rate of a silicon nitride layer is obtainable, and a polishing method employing such a composition. A polishing composition which has silicon oxide abrasive grains, an acidic additive and water, wherein the acidic additive is such that when it is formed into a 85 wt % aqueous solution, the chemical etching rate of the silicon nitride layer is at most 0.1 nm/hr in an atmosphere of 80° C. Particularly preferred is one wherein the silicon oxide abrasive grains have an average particle size of from 1 to 50 nm, and the pH of the composition is from 3.5 to 6.5.

Claims

1. A polishing composition to be used in a step of polishing a silicon nitride layer until a silicon oxide layer is reached in polishing for production of a semiconductor, which comprises silicon oxide abrasive grains, an acidic additive and water, wherein the acidic additive is such that when it is formed into a 85 wt % aqueous solution, a chemical etching rate of the silicon nitride layer is at most 0.1 nm/hr in an atmosphere of 80°

C.

2. The polishing composition according to claim 1, wherein the silicon oxide abrasive grains have an average particle size of from 1 to 50 nm as calculated from specific surface area measured by BET method.

3. The polishing composition according to claim 1, wherein the acidic additive is at least one member selected from the group consisting of hydrochloric acid, sulfuric acid, formic acid, acetic acid, oxalic acid, adipic acid and lactic acid.

4. The polishing composition according to claim 1, wherein as calculated from a stock removal rate of the silicon nitride layer by said polishing composition and a stock removal rate of the silicon oxide layer by a standard polishing composition having the following composition:

fumed silica abrasive grains (average particle size;

20 to 40 nm);

12 wt %,

aqueous ammonia (28%);

0.5%, and

water;

rest,

the ratio of (the stock removal rate of the silicon nitride layer)/(the stock removal rate of the silicon oxide layer when the standard polishing composition is used) is at least ¼

.

5. The polishing composition according to claim 1, wherein as calculated from a stock removal rate of the silicon nitride and a stock removal rate of the silicon oxide layer under the same polishing conditions, the ratio of (the stock removal rate of the silicon nitride layer)/(the stock removal rate of the silicon oxide layer) is at least 3.

6. The polishing composition according to claim 1, wherein the silicon oxide abrasive grains are present in an amount of 0.1 to 20 wt % based on the weight of the composition.

7. The polishing composition according to claim 6, wherein the silicon oxide abrasive grains are present in an amount of 1 to 10 wt % based on the weight of the composition.

8. The polishing composition according to claim 1, which as a pH of from 3.5 to 6.5.

9. The polishing composition according to claim 8, which as a pH of from 4 to 5.

10. The polishing composition according to claim 1, wherein the chemical etching rate of the silicon nitride layer is at most 0.01 nm/hr in an atmosphere of 80°

C.

11. The polishing composition according to claim 5, wherein the ratio is at least 10.

12. A polishing method which comprises polishing a substrate provided with a silicon nitride layer and a silicon oxide layer, with the polishing composition as defined in claim 1, in polishing for the production of a semiconductor, wherein the silicon nitride layer is polished until the polishing reaches the silicon oxide layer.