CMP compositions exhibiting reduced dishing in STI wafer polishing
The invention provides a chemical-mechanical polishing composition containing a ceria abrasive, an ionic polymer of formula I: wherein X 1 and X 2 , Z 1 and Z 2 , R 1 , R 2 , R 3 , and R 4 , and n are as defined herein, a polyhydroxy aromatic compound, a polyvinyl alcohol, and water, wherein the polishing composition has a pH of about 1 to about 4.5. The invention further provides a method of chemically-mechanically polishing a substrate with the inventive chemical-mechanical polishing composition. Typically, the substrate contains silicon oxide, silicon nitride, and/or polysilicon.
1. A chemical-mechanical polishing composition comprising:
(a) a wet-process ceria abrasive,
(b) an ionic polymer of formula (I):
wherein X 1 and X 2 are independently selected from hydrogen, —OH, and —COOH and wherein at least one of X 1 and X 2 is —COOH,
Z 1 and Z 2 are independently O or S,
R 1 , R 2 , R 3 , and R 4 are independently selected from hydrogen, C 1 -C 6 alkyl, and C 7 -C 10 aryl, and
n is an integer of about 3 to about 500,
(c) a polyhydroxy aromatic compound,
(d) a polyvinyl alcohol, and
(e) water,
wherein the polishing composition has a pH of about 1 to about 4.5.
2. The polishing composition of claim 1 , wherein X 1 and X 2 are both —COOH.
3. The polishing composition of claim 2 , wherein Z 1 and Z 2 are both O, and R 1 , R 2 , R 3 , and R 4 are hydrogen.
4. The polishing composition of claim 1 , wherein the ionic polymer has a molecular weight of about 500 daltons to about 10,000 daltons, and wherein n is an integer with a value of 8 or greater.
5. The polishing composition of claim 1 , wherein the ionic polymer is present in an amount of about 0.01 wt. % to about 0.5 wt. % of the polishing composition.
6. The polishing composition of claim 1 , wherein the wet-process ceria abrasive is present in an amount of about 0.05 wt. % to about 1 wt. % of the polishing composition.
7. The polishing composition of claim 1 , wherein the polyvinyl alcohol has a molecular weight of about 20,000 daltons to about 200,000 daltons.
8. The polishing composition of claim 1 , wherein the polyvinyl alcohol is a branched polyvinyl alcohol.
9. The polishing composition of claim 1 , wherein the polyhydroxy aromatic compound is selected from 1,3-dihydroxybenzene and 1,3,5-trihydroxybenzene.
10. A method of chemically-mechanically polishing a substrate comprising:
(i) contacting a substrate with a polishing pad and a chemical-mechanical polishing composition comprising:
(a) a wet-process ceria abrasive,
(b) an ionic polymer of formula (I):
wherein X 1 and X 2 are independently selected from hydrogen, —OH, and —COOH and wherein at least one of X 1 and X 2 is —COOH,
Z 1 and Z 2 are independently O or S,
R 1 , R 2 , R 3 and R 4 are independently selected from hydrogen, C 1 -C 6 alkyl, and C 7 -C 10 aryl, and
n is an integer of about 3 to about 500,
(c) a polyhydroxy aromatic compound,
(d) a polyvinyl alcohol, and
(e) water,
wherein the polishing composition has a pH of about 1 to about 4.5,
(ii) moving the polishing pad and the chemical-mechanical polishing composition relative to the substrate, and
(iii) abrading at least a portion of the substrate to polish the substrate.
11. The method of claim 10 , wherein X 1 and X 2 are both —COOH.
12. The method of claim 11 , wherein Z 1 and Z 2 are both O, and R 1 , R 2 , R 3 , and R 4 are hydrogen.
13. The method of claim 10 , wherein the ionic polymer has a molecular weight of about 500 daltons to about 10,000 daltons, and wherein n is an integer with a value of 8 or greater.
14. The method of claim 10 , wherein the ionic polymer is present in an amount of about 0.01 wt. % to about 0.5 wt. % of the polishing composition.
15. The method of claim 10 , wherein the wet-process ceria abrasive is present in an amount of about 0.1 wt. % to about 1 wt. % of the polishing composition.
16. The method of claim 10 , wherein the polyvinyl alcohol has a molecular weight of about 20,000 daltons to about 200,000 daltons.
17. The method of claim 10 , wherein the polyvinyl alcohol is a branched polyvinyl alcohol.
18. The method of claim 10 , wherein the polyhydroxy aromatic compound is selected from 1,3-dihydroxybenzene and 1,3,5-trihydroxybenzene.
19. The method of claim 10 , wherein the substrate comprises silicon oxide, and wherein at least a portion of the silicon oxide is abraded to polish the substrate.
20. The method of claim 19 , wherein the substrate further comprises silicon nitride, and wherein at least a portion of the silicon nitride is abraded to polish the substrate.
21. The method of claim 19 , wherein the substrate further comprises polysilicon, and wherein at least a portion of the polysilicon is abraded to polish the substrate.