Positive resist composition for immersion exposure and pattern-forming method using the same

A positive resist composition for immersion exposure comprising:

• (A) a resin capable of increasing its solubility in an alkali developer by an action of an acid, and
• (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation,
• wherein the acid satisfies conditions of V≧230 and V/S≦0.93 taking van der Waals volume of the acid as V (Å3), and van der Waals surface area of the acid as S (Å2)
• wherein the compound (B) comprises a sulfonium salt compound having an anion represented by formula (Y):
• in formula (Y), n3 represents an integer of from 3 to 6 and n4 represents an integer of from 3 to 6, and
• a sulfonium salt compound having an anion represented by formula (X):
• in formula (X), Rx represents an alkyl group, —OR′1, —C(═O)R′1, —C(═O)OR′1, —SO2R′1, or —SO3R′1;
• Ay represents a single bond, —SO2—, —SO3—, —SO2N(R′1) —, —CO2—, —C(═O)—, —C(═O)N(R′1)—, or an alkylene group;
• R′1 represents a hydrogen atom or an alkyl group;
• Az represents a monocyclic or polycyclic hydrocarbon group, or an aryl group;
• n1 represents an integer of from 1 to 4;
• and n2 represents an integer of from 1 to 4.

A pattern-forming method comprising:

• forming a resist film with a positive resist composition for immersion exposure comprising:
• (A) a resin capable of increasing its solubility in an alkali developer by an action of an acid, and
• (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation,
• wherein the acid satisfies conditions of V≧230 and V/≦0.93 taking van der Waals volume of the acid as V (Å3), and van der Waals surface area of the acid as S (Å2);
• exposing the resist film through an immersion liquid so as to form an exposed resist film;
• and
• developing the exposed resist film
• and wherein the compound (B) is a sulfonium salt compound having an anion represented by formula (X):
• in formula (X), Rx represents an alkyl group, —OR′1, —C(═O)R′1, —C(═O)OR′1, —SO2R′1, or —SO3R′1;
• Ay represents a single bond, —SO2—, —SO3—, —SO2N(R′1)—, —CO2—, an oxygen atom, —C(═O)—, —C(═O)N(R′1)—, or an alkylene group;
• R′1 represents a hydrogen atom or an alkyl group;
• Az represents an aliphatic monocyclic or polycyclic hydrocarbon group;
• n1 represents an integer of from 1 to 4;
• and n2 represents an integer of from 1 to 4.