Positive resist composition and pattern forming method using the resist composition

1. A positive resist composition comprising:

(A) a resin insoluble or sparingly soluble in an alkali but capable of decomposing under an action of an acid to increase a solubility in an alkali developer, the resin having a β-(meth)acroyloxy-γ-butyrolactone repeating unit represented by the following formula (1) containing a lactone ring which may have a substituent; and

(B) a compound capable of generating an organic acid represented by the following formula (2), (3), (3′), (4) or (5) upon irradiation of actinic rays or radiation:

wherein R 1 represents a hydrogen atom or an alkyl group, and the lactone ring may have a substituent;

wherein

Rf represents an organic group having a fluorine atom,

R represents a hydroxyl group or an organic group,

Ar represents an aromatic group,

l represents an integer of 1 to 6,

m represents an integer of 0 to 4, and

n represents an integer of 0 to 4,

provided that m+n represents an integer of 1 or more;

wherein

A 1 represents a divalent linking group,

A 2 and A 3 each independently represents a single bond, an oxygen atom or —N(Rx)-,

Rx represents a hydrogen atom, an aryl group, an alkyl group or a cycloalkyl group,

A 4 represents a single bond or —C(═O)—,

Ra represents a hydrogen atom or an organic group,

p represents 2 or 3,

Rb represents a p-valent linking group, and

when A 3 is —N(Rx)-, Ra and Rx, or Rb and Rx may combine to form a ring; and

wherein

Y represents an alkylene group substituted by at least one fluorine atom, and

Rc represents an alkyl group or a cycloalkyl group.

2. The positive resist composition as claimed in claim 1 , further comprising a dissolution inhibiting compound having a molecular weight of 3,000 or less and capable of decomposing under an action of an acid to increase a solubility in an alkali developer.

3. The positive resist composition as claimed in claim 2 , wherein the dissolution inhibiting compound has a molecular weight of 300 to 3,000.

4. The positive resist composition as claimed in claim 2 , wherein the dissolution inhibiting compound has a molecular weight of 500 to 2,500.

5. The positive resist composition as claimed in claim 1 , further comprising a basic compound.

6. The positive resist composition as claimed in claim 5 , wherein the basic compound is as organic amine, basic ammonium salt, basic sulfonium salt and basic iodonium salt.

7. A pattern forming method comprising steps of forming a resist film from the positive resist composition claimed in claim 1 , and exposing and developing the resist film.