Positive resist composition and method of forming resist pattern using the same.

1. A positive resist composition comprising:

(A) a fluorine atom-containing resin,

wherein the resin comprises at least one group that increases a solubility of the resin in an alkali developer by the action of an acid; and

(B) a sulfonium salt compound represented by the following general formula (A) which generates an acid upon irradiation with one of an actinic ray and a radiation:

wherein Ra 1 represents a hydroxy group, a halogen atom, an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aryl group, an aryloxy group, an acyl group, an acylamino group, or an alkylsulfonylamino group, provided that when two or more Ra 1 's are present in the molecule, these are the same or different; 1, m, and n each represents an integer of 0 to 4; and X − represents a non-nucleophilic anion.

2. The positive resist composition of claim 1 , wherein the resin (A) is a resin which has repeating a unit having a group represented by the following general formula (Z):

wherein R 50 to R 55 each independently represents a hydrogen atom, a fluorine atom, or an alkyl group, provided that at least one of R 50 to R 55 represents either a fluorine atom or an alkyl group in which at least one of the hydrogen atoms has been replaced by a fluorine atom; and Rx represents a hydrogen atom or an organic group.

3. The positive resist composition of claim 1 , wherein the resin (A) includes a repeating unit and the repeating unit includes a group where a carboxyl group is protected by an acid-decomposable group.

4. The positive resist composition of claim 1 , wherein the resin (A) has a weight-average molecular weight of from 1,000 to 200,000, and the resin (A) has no more than 10% by weight of a total amount of a component having a molecular weight of 1,000 or lower.

5. The positive resist composition of claim 1 , further comprising:

(C) a fluorochemical surfactant or silicone surfactant; and

(D) a basic compound.

6. The positive resist composition of claim 5 , wherein the basic compound (D) is a compound having a structure selected from an imidazole structure, diazabicyclo structure, onium hydroxide structure, onium carboxylate structure, trialkylamine structure, and aniline structure.

7. The positive resist composition of claim 1 , further comprising (F) a dissolution-inhibiting compound having a molecular weight of not more than 3,000 which is capable of decomposing by the action of an acid to increase solubility in an alkali developer.

8. The positive resist composition of claim 1 , wherein said at least one group, that increases a solubility of the resin in an alkali developer by the action of an acid, is a group causing an alkali-soluble group by the action of an acid.

9. A method of forming a resist pattern comprising:

coating the positive resist composition as described in claim 1 on a substrate;

irradiating a resultant coating with actinic rays or a radiation; and

developing the resultant coating.

10. The positive resist composition of claim 1 , wherein at least one of the Ra 1 groups in formula (A) is not a hydrogen atom.

11. The positive resist composition of claim 1 , wherein at least one of the Ra 1 groups on an aromatic ring group having a hydroxyl group in formula (A) is an alkyl group.

12. The positive resist composition of claim 1 , wherein X − in formula (A) is selected from the group consisting of a nonafluorobutanesulfonic acid anion, a perfluorooctanesulfonic acid anion, a bis(alkylsulfonyl)imide anion, a tris(alkylsulfonyl)methyl anion, a benzenesulfonic acid anion substituted with one or more fluorine atoms, and a benzenesulfonic acid anion substituted with a group having one or more fluorine atoms.