Photosensitive composition and pattern forming method using the same

1. A photoresist composition comprising (A) a resin that is decomposed by the action of an acid to increase solubility in an alkali developing solution, (B) a compound that generates an acid upon irradiation of an actinic ray or radiation, and (C1) a nonionic compound having a molecular weight of 1,000 or less and containing an aliphatic ring and a phenol ring,

wherein the resin (A) comprises a repeating unit having a group represented by the following formula (I) and a repeating unit which has a group represented by at least one of the following formulae (V-I) to (V-4) or which is represented by the following formula (IV):

wherein R 2 to R 4 each independently represents a hydrogen atom or a hydroxy group, provided that at least one of R 2 to R 1 represents a hydroxy group,

R 1b to R 5b each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an alkenyl group, or two of R 1b to R 5b may be connected to each other to form a ring,

R 1a represents a hydrogen atom or a methyl group,

W 1 represents an individual group or a combination of two or more groups, selected from a single bond, an alkylene group, an ether group, a thioether group, a carbonyl group and an ester group,

R a1 , R b1 , R c1 , R d1 and R e1 each independently represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, and

m and n each independently represents an integer of from 0 to 3, provided that m+n is from 2 to 6, and

wherein the photoresist composition is suitable for exposure with an ArF excimer laser.

2. A photoresist composition comprising (A) a resin that is decomposed by the action of an acid to increase solubility in an alkali developing solution, (B) a compound that generates an acid upon irradiation of an actinic ray or radiation, and (C2) a resin containing a hydroxystyrene unit,

wherein the resin (A) contains a repeating unit including an alicyclic group that is decomposed by the action of an acid to increase solubility in an alkali developing solution, the alicyclic group having 7 to 25 carbon atoms,

a repeating unit having a group represented by the following formula (I):

wherein R 2c to R 4c each independently represents a hydrogen atom or a hydroxy group, provided that at least one of R 2c to R 4c represents a hydroxy group, and

a repeating unit which has a group represented by at least one of the following formulae (V-I) to (V-4) or which is represented by the following formula (IV):

wherein R 1b to R 5b each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an alkenyl group, or two of R 1b to R 5b may be connected to each other to form a ring,

R 1a represents a hydrogen atom or a methyl group,

W 1 represents an individual group or a combination of two or more groups selected from a single bond, an alkylene group, an ether group, a thioether group, a carbonyl group and an ester group,

R a1 , R b1 , R c1 , R d1 and R e1 each independently represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, and

m and n each independently represents an integer of from 0 to 3, provided that m+n is from 2 to 6, and

wherein the photoresist composition is suitable for exposure with an ArF excimer laser.

3. The photoresist composition as claimed in claim 2 , wherein the resin (C2) has a molecular weight distribution of 2.0 or less.

4. The photoresist composition as claimed in claim 2 , wherein the resin (C2) is a resin wherein a part of hydroxy groups of polyhydroxystyrene are protected with a group decomposable by a reaction with an acid.

5. The photoresist composition as claimed in claims 2 , wherein the resin (C2) is a copolymer containing at least a hydroxystyrene unit and a unit wherein a carboxy group in methacrylic acid or acrylic acid is protected with an alicyclic group decomposable by an acid.

6. A positive pattern forming method comprising forming a photosensitive layer having a dry layer thickness of 250 nm or less comprising the photoresist composition as claimed in claim 1 on a substrate, exposing the photosensitive layer to an actinic ray or radiation having a wavelength of 200 nm or shorter, subjecting the exposed photosensitive layer to heat treatment at 150° C. or lower, and then developing the heat-treated photosensitive layer with an alkali developing solution.

7. A positive pattern forming method comprising forming a photosensitive layer having a dry layer thickness of 250 nm or less comprising the photoresist composition as claimed in claim 2 on a substrate, exposing the photosensitive layer to an actinic ray or radiation having a wavelength of 200 nm or shorter, subjecting the exposed photosensitive layer to heat treatment at 150° C. or lower, and then developing the heat-treated photosensitive layer with an alkali developing solution.

8. The photoresist composition as claimed in claim 1 , wherein the resin (A) contains a repeating unit including an alicyclic group that is decomposed by the action of an acid to increase solubility in an alkali developing solution, the alicyclic group having 7 to 25 carbon atoms.

9. The photoresist composition as claimed in claim 1 , wherein the resin (A) comprises a repeating unit having a group represented by the following formula (AII):

wherein R 1c represents a hydrogen atom or a methyl group, and

R 2c to R 4c each independently represents a hydrogen atom or a hydroxy group, provided that at least one of R 2c to R 4c represents a hydroxy group.

10. The photoresist composition as claimed in claim 2 , wherein the resin (A) comprises a repeating unit having a group represented by the following formula (AII):

wherein R 1c represents a hydrogen atom or a methyl group, and

R 2c to R 4c each independently represents a hydrogen atom or a hydroxy group, provided that at least one of R 2c to R 4c represents a hydroxy group.