Positive resist composition and process for forming pattern using the same

1. A positive resist composition comprising:

(A) a resin containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), the resin being insoluble or slightly soluble in an alkali developer and becoming soluble in an alkali developer by an action of an acid,

(B) a compound generating a sulfonic acid compound represented by the following formula (3) upon irradiation of actinic ray or radiation, and

(C) a compound generating a non-aromatic sulfonic acid compound upon irradiation of actinic ray or radiation,

wherein R 01 represents a hydrogen atom, a methyl group, a cyano group, a halogen atom or a perfluoro group having from 1 to 4 carbon atoms,

R 02 and R 03 each independently represents an alkyl group, and

X represents an acid decomposable group having an alicyclic group,

wherein R 04 represents a hydrogen atom or a methyl group,

R 05 represents a hydrogen atom, an alkyl group, a halogen atom, an aryl group, an alkoxy group or an acyl group, and

n represents an integer of from 0 to 4,

wherein Ra to Re each independently represents a hydrogen atom, an unsubstituted alkyl group or an alkyl group substituted with an aryl group, a hydroxyl group or an alkoxy group, a cycloalkyl group, an alkoxy group, a hydroxyl group, a carboxyl group, an alkyloxycarbonyl group, an alkylcarbonyloxy group, an aryl group or an aralkyl group,

wherein the resin (A) further contains a repeating unit represented by the following formula (4):

wherein R 04 , R 05 and n have the same meanings as R 04 , R 05 and n in formula (2) respectively, and W represents a group that is not decomposed by an action of an acid.

2. The positive resist composition as claimed in claim 1 , which further comprises an organic basic compound.

3. The positive resist composition as claimed in claim 1 , wherein X in formula (1) represents a bridged alicyclic group.

4. The positive resist composition as claimed in claim 3 , wherein the bridged alicyclic group represented by X in formula (1) is an adamantyl group.

5. The positive resist composition as claimed in claim 1 , which further comprises a fluorine surfactant and/or a silicone surfactant.

6. A process for forming a pattern comprising steps of: forming a resist film with the positive resist composition as claimed in claim 1 ; exposing the resist film; and developing the exposed resist film.

7. The positive resist composition as claimed in claim 1 , wherein the content of the sulfonic acid generator (B) is from 5 to 20% by weight.

8. The positive resist composition as claimed in claim 1 , wherein the non-aromatic sulfonic acid generated by the acid generator (C) is an alkylsulfonic acid having from 2 to 20 carbon atoms, which may have a substituent.

9. The positive resist composition as claimed in claim 1 , wherein the weight ratio of the sulfonic acid generator (B) to the sulfonic acid generator (C) is at least 5/95.

10. The positive resist composition as claimed in claim 1 , wherein the weight ratio of the sulfonic acid generator (B) to the sulfonic acid generator (C) is at least 20/80.

11. The positive resist composition as claimed in claim 1 , wherein the weight ratio of the sulfonic acid generator (B) to the sulfonic acid generator (C) is at least 40/60.