Reverse Shallow Trench Isolation Process

Abstract

A method of polishing a substrate surface containing silicon nitride and silicon oxide or silicon dioxide, comprising movably contacting the surface with a polishing pad and having a polishing composition disposed between the polishing pad and the surface, said polishing composition comprising 1) hydrous ceria abrasive; 2) polyvinylpyridine, vinyl pyridine copolymers, or both, and 3) water, wherein at 2 psi downpressure the silicon nitride removal rate is at least 500 angstroms per minute and the selectivity of silicon nitride to silicon oxide is at least 30.

1 . A method of polishing a substrate surface containing silicon nitride and silicon oxide, comprising movably contacting the surface with a polishing pad and having a polishing composition disposed between the polishing pad and the surface, said polishing composition comprising 1) hydrous ceria abrasive; 2) polyvinylpyridine, vinyl pyridine copolymers having more than 60 molar percent of monomers being vinyl pyridine, or both, and 3) water, wherein the polishing composition comprises at least 60 ppm of poly(4-vinylpyridine). 
   
   
       2 . The method of  claim 1  wherein the polishing composition comprises at least 80 ppm of poly(4-vinylpyridine). 
   
   
       3 . The method of  claim 1  wherein the polishing composition comprises between 100 and 200 ppm of poly(4-vinylpyridine). 
   
   
       4 . The method of  claim 1  wherein the polishing composition comprises poly(4-vinyl pyridine co-styrene). 
   
   
       5 . The method of  claim 1  wherein the silicon nitride to silicon oxide selectivity is at least 30, and wherein the silicon nitride removal rate is at least 500 angstroms per minute. 
   
   
       6 . The method of  claim 1  wherein the silicon nitride to silicon oxide selectivity is at least 40, and wherein the silicon nitride removal rate is at least 600 angstroms per minute when polished at a 2 psi downpressure. 
   
   
       7 . The method of  claim 1  wherein the silicon nitride to silicon oxide selectivity is at least 60. 
   
   
       8 . The method of  claim 1  wherein the polishing composition is at pH 3.9 to 4.1. 
   
   
       9 . The method of  claim 1  wherein the silicon nitride to silicon oxide selectivity is variable from 0.8 to over 50 by changing only the amount of polyvinylpyridine, vinyl pyridine copolymers, or both present in the polishing composition. 
   
   
       10 . The method of  claim 1  wherein the polishing composition comprises 1) about 0.05% to 2% by weight of hydrous ceria; 2) more than 60 to about 300 ppm of one or more of poly(4-vinylpyridine), a polymer made from monomers consisting essentially of 4-vinylpyridine, poly(4-vinylpyridine co-styrene), other 4-vinylpyridine-based copolymers, or mixture thereof; and 3) water. 
   
   
       11 . The method of  claim 1  wherein the polishing composition comprises 1) about 0.05% to 2% by weight of hydrous ceria; 2) 80 to about 600 ppm of one or more of poly(4-vinylpyridine), a polymer made from monomers consisting essentially of 4-vinylpyridine, poly(4-vinylpyridine co-styrene), other 4-vinylpyridine-based copolymers, or mixture thereof; and 3) high purity water, wherein the pH is between 3.5 and 4.5. 
   
   
       12 . The method of  claim 1  wherein the polishing composition consists essentially of 1) about 0.05% to 2% by weight of hydrous ceria; 2) 80 to about 600 ppm poly(4-vinylpyridine); and 3) high purity water, wherein the pH is between 3.8 and 4.2. 
   
   
       13 . The method of  claim 1  wherein the polishing composition consists essentially of 1) about 0.05% to 2% by weight of hydrous ceria; 2) 80 to about 600 ppm of a copolymer containing at least 70 molar percent of 4-vinylpyridine copolymerized with other polymers, poly(4-vinylpyridine), or mixture thereof; and 3) high purity water. 
   
   
       14 . A method of polishing a substrate surface containing silicon nitride and silicon oxide, comprising movably contacting the surface with a polishing pad and having a polishing composition disposed between the polishing pad and the surface, said polishing composition comprising 1) hydrous ceria abrasive; 2) polyvinylpyridine, vinyl pyridine copolymers, or both, and 3) water, wherein at 2 psi downpressure the silicon nitride removal rate is at least 500 angstroms per minute and the selectivity of silicon nitride to silicon oxide is at least 30 and wherein the polishing composition comprises at least 60 ppm of poly(4-vinylpyridine). 
   
   
       15 . The method of  claim 14  wherein the selectivity of silicon nitride to silicon oxide at 2 psi downpressure is at least 40. 
   
   
       16 . The method of  claim 15  wherein the hydrous ceria was provided by milling submicron ceria in an aqueous milling medium of no high purity alpha alumina at a pH of between 10 and 11 for a time sufficient to allow the hydroxyl ions to react with the surface of the ceria. 
   
   
       17 . The method of  claim 15  wherein the polishing composition contains substantially no polydiallyldimethylammonium halide, poly(amidoamine), poly(methacryloyloxyethyltrimethylammonium) chloride, poly(methacryloyloxyethyldimethylbenzylammonium) chloride, poly(vinylpyrrolidone), poly(vinylimidazole), poly(vinylamine), and copolymers of acrylamide and diallyldimethylammonium chloride. 
   
   
       18 . The method of  claim 15  wherein the polishing composition contains no oxidizing agents. 
   
   
       19 . The method of  claim 15  wherein the polishing composition contains less than 20 ppm total of chloride and fluoride. 
   
   
       20 . The method of  claim 15  wherein the polishing composition additionally comprises between 0.005% and 0.1% of an ethoxylated fluorosurfactant.