Positive photoresist composition

A positive photoresist composition comprising (A) a resin which comprises

• (a) a repeating unit represented by formula (I) shown below,
• (b) at least one repeating unit represented by formula (IIa) or (IIb) shown below,
• (c) a repeating unit represented by formula (III) shown below, and
• (d) a repeating unit represented by formula (IV) and which satisfies the following conditions (i)-(iii):
• (i) Is copolymerizable with monomers corresponding to the repeating units represented by formulae (I) to (III);
• (ii) Contains at least one functional group selected from the group consisting of a group containing a lactone structure, a group containing a lactam structure, —OH, —OCH3, —OCORa, —NHCORa, —NHSO2Ra, —N(R)CORa, —N(R)SO2Ra, —COOH, —COORa, —CONHRa, —CONHSO2Ra, —CON(R)SO2Ra, —CON(Ra)(Rb) and —CN, wherein R, Ra and Rb each independently represents an alkyl or aryl group having from 1 to 10 carbon atoms, which may be substituted;
• and
• (iii) Is substantially incapable of decomposing by an acid,
• and which increases in the solubility in an alkali developer under the action of an acid:
• wherein R1 to R3 each independently represents an alkyl group, a haloalkyl group, a halogen atom, an alkoxy group, a trialkylsilyl group or a trialkylsilyloxy group, and n represents 0 or 1;
• wherein Y represents a group selected from the group consisting of a hydrogen atom, a methyl group, a cyano group and a chlorine atom, L represents a single bond or a divalent linking group, and Q represents a hydrogen atom or a group capable of decomposing by an acid to generate a carboxylic acid;
• wherein X1 and X2 each independently represents a group selected from an oxygen atom, a sulfur atom, —NH— and —NHSO2—;
• L1 and L2 each independently represents a single bond or a divalent linking group;
• A1 represents —Q′ or —COOQ′, provided that when X1 represents an oxygen atom and L1 represents a single bond, A1 represents —Q′;
• A2 represents a hydrogen atom, a cyano group, a hydroxyl group, —COOH, —COOR′, —CO—NH—R″, an alkyl group which may be substituted, a cyclic hydrocarbon group which may be substituted, an alkoxy group or —COOQ′, wherein R′ and R″ each independently represents an alkyl group which may have a substituent;
• and Q′ represents a group capable of decomposing by an acid to generate a carboxylic acid;
• wherein Z represents an oxygen atom or N-R4, R4 represents a hydrogen atom, a hydroxyl group, an alkyl group having a linear or branched chain, or —O—SO2—R5, and R5 represents an alkyl group or a trihalomethyl group;
• wherein Y represents a group selected from the group consisting of a hydrogen atom, a methyl group, a cyano group and a chlorine atom, X3 represents a group selected from the group consisting of —CO2—, —O— and —CON(R)—, wherein R has the same meaning as above, L3 represents a single bond or a divalent linking group, and A3 represents a group represented by the following formula (V) or (VI)
• —X4—(Rc)m1 (V)
• wherein X4 represents an alicyclic hydrocarbon group which may contain a carbonyl bond or an ester bond within the ring, each Rc independently represents a hydrogen atom, an alkyl group, an alkyl group containing as a substituent at least one functional group selected from the group consisting of —OH, —OCH3, —OCORa, —NHCORa, —NHSO2Ra, —N(R)CORa, —N(R)SO2Ra, —COOH, —COORa, —CONHRa, —CONHSO2Ra, —CON(R)SO2Ra, —CON(Ra)(Rb) and —CN, or a group selected from the group consisting of —OH, —OCH3, —OCORa, —NHCORa, —NHSO2Ra, —N(R)CORa, —N(R)SO2Ra, —COOH, —COORa, —CONHRa, —CONHSO2Ra, —CON(R)SO2Ra, —CON(Ra)(Rb) and —CN, wherein R, Ra and Rb each has the same meaning as above, and m1 represents an integer of 0 to 5;
• wherein Rc1 and Rc3 each independently represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, which may be substituted, an alkyl group containing as a substituent at least one functional group selected from the group consisting of —OH, —OCH3, —OCORa, —NHCORa, —NHSO2Ra, —N(R)CORa, —N(R)SO2Ra, —COOH, —COORa, —CONHRa, —CONHSO2Ra, —CON(R)SO2Ra, —CON(Ra)(Rb) and —CN, or a group selected from the group consisting of —COOH, —COORa, —CONHRa, —CONHSO2Ra, —CON(R)SO2Ra, —CON(Ra)(Rb) and —CN, provided that Rc1 and Rc3 are not simultaneously hydrogen;
• and Rc2 represents a group selected from the group consisting of —OH, —OCH3, —OCORa, —NHCORa, —NHSO2Ra, —N(R)CORa, —N(R)SO2Ra, —COOH, —COORa, —CONHRa, —CONHSO2Ra, —CON(R)SO2Ra, —CON(Ra)(Rb) and —CN, wherein R, Ra and Rb each has the same meaning as above.