Positive resist composition and patterning process

1. A chemically amplified positive resist composition comprising a polymer comprising repeat units having the general formula (3) or (4):

wherein

denotes a substituted or unsubstituted aromatic hydrocarbon group, R 1 is each independently hydrogen, methyl or trifluoromethyl, R 2 is a straight, branched or cyclic C 1 -C 12 alkyl or aromatic hydrocarbon group, R 3 is a straight, branched or cyclic C 1 -C 12 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, wherein R 2 and R 3 , taken together, denote a C 5 -C 12 alkylene group, R 4 is hydrogen or methyl, a is 1 or 2, b is an integer of 1 to 5, m, n, and p are numbers in the range: 0≦m<1.0, 0<n<1.0, and 0.08≦p<0.5.

2. A process for forming a pattern, comprising the steps of applying the positive resist composition of claim 1 onto a substrate to form a resist coating; heat treating the resist coating, then exposing it to high-energy radiation, EUV or electron beam through a photomask; and optionally heat treating the exposed resist coating, then developing with a developer.

3. A process for forming a pattern, comprising the steps of applying the positive resist composition of claim 1 onto a substrate to form a resist coating; heat treating the resist coating, then exposing it to high-energy radiation or electron beam through a photomask; and heat treating the exposed resist coating, then developing with a developer,

said exposing step being performed by immersion lithography including holding a high refractive index liquid having a refractive index of at least 1.0 between the resist coating and a projection lens.

4. A process for forming a pattern, comprising the steps of applying the positive resist composition of claim 1 onto a substrate to form a resist coating, heat treating the resist coating, forming a protective film on the resist coating, exposing the resist coating to high-energy radiation or electron beam through a photomask, heat treating the exposed resist coating, and developing with a developer,

said exposing step being performed by immersion lithography including holding a high refractive index liquid having a refractive index of at least 1.0 between the protective film and a projection lens.

5. A photomask blank comprising a chromium compound film and a coating of the resist composition of claim 1 thereon.

6. A process for forming a pattern, comprising the steps of heat treating the photomask blank of claim 5 , subjecting the resist coating to patternwise exposure to high-energy radiation through a photomask or patternwise exposure to high-energy beam, optionally heat treating the exposed resist coating, and developing it with a developer.

7. The composition of claim 1 wherein p is a number in the range of 0.1≦p<0.5.

8. A chemically amplified positive resist composition comprising a polymer comprising repeat units having the general formula (5) or (6):

wherein

denotes a substituted or unsubstituted aromatic hydrocarbon group, R 1 is each independently hydrogen, methyl or trifluoromethyl, R 2 is a straight, branched or cyclic C 1 -C 12 alkyl or aromatic hydrocarbon group, R 3 is a straight, branched or cyclic C 1 -C 12 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, wherein R 2 and R 3 , taken together, denote a C 5 -C 12 alkylene group, R 4 is hydrogen or methyl, R 5A is an acid labile group, a is 1 or 2, b and c each are an integer of 1 to 5, m1, m2, n, and p are numbers in the range: 0<m1<1.0, 0<m2<1.0, 0<n<1.0, and 0.08≦p<0.5.

9. The composition of claim 8 wherein p is a number in the range of 0.1≦p<0.5.

10. A positive resist composition comprising a polymer comprising repeat units having the general formula (11) or (12):

wherein

denotes a substituted or unsubstituted aromatic hydrocarbon group, R 1 is each independently hydrogen, methyl or trifluoromethyl, R 2 is hydrogen or a straight, branched or cyclic C 1 -C 12 alkyl or aromatic hydrocarbon group, R 3 is a straight, branched or cyclic C 1 -C 12 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, wherein R 2 and R 3 , taken together, denote a C 5 -C 12 alkylene group, R 5A is an acid labile group, R 5B is a lactone-containing adhesive group, R 6 is a substituent group of the formula (13) or (14):

wherein R 7 is a divalent C 1 -C 20 hydrocarbon group which may contain a heteroatom, R 8 is a single bond, a C 1 -C 4 alkylene, or a substituted C 1 -C 4 alkylene in which all or some hydrogen atoms are substituted by fluorine, R 9 and R 10 are each independently hydrogen, fluorine, a C 1 -C 4 alkyl, or a substituted C 1 -C 4 alkyl in which all or some hydrogen atoms are substituted by fluorine, at least either one of R 9 and R 10 contains fluorine, or either one of R 9 and R 10 may bond with R 8 to form a ring, and d is 1 or 2,

where

denotes a C 3 -C 12 cyclic hydrocarbon group or a bridged cyclic hydrocarbon group, which may contain hydroxyl, —O— or —S—, R 11 , R 12 and R 13 are each independently hydrogen, fluorine or trifluoromethyl, at least either one of R 11 , R 12 and R 13 contains at least one fluorine atom,

a is 1 or 2, r, s, t, u and v are numbers in the range: 0<r<1.0, 0<s≦0.8, 0<t≦0.8, 0<u≦0.2, and 0<v≦0.2.

11. A chemically amplified positive resist composition comprising

(A) an organic solvent,

(B) a base resin comprising a polymer,

(C) a photoacid generator, and

(D) a basic compound;

wherein the polymer comprises repeat units having the general formula (3) or (4):

wherein

denotes a substituted or unsubstituted aromatic hydrocarbon group, R 1 is each independently hydrogen, methyl or trifluoromethyl, R 2 is a straight, branched or cyclic C 1 -C 12 alkyl or aromatic hydrocarbon group, R 3 is a straight, branched or cyclic C 1 -C 12 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, wherein R 2 and R 3 , taken together, denote a C 5 -C 12 alkylene group, R 4 is hydrogen or methyl, a is 1 or 2, b is an integer of 1 to 5, m, n, and p are numbers in the range: 0≦m<1.0, 0<n<1.0, and 0.08≦p<0.5.

12. A chemically amplified positive resist composition comprising a polymer comprising repeat units having the general formula (3′) or (4′):

wherein

denotes a substituted or unsubstituted aromatic hydrocarbon group, R 1 is each independently hydrogen, methyl or trifluoromethyl, R 2 is a straight, branched or cyclic C 1 -C 12 alkyl or aromatic hydrocarbon group, R 3 is a straight, branched or cyclic C 1 -C 12 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, wherein R 2 and R 3 , taken together, denote a C 5 -C 12 alkylene group, R 4 is hydrogen or methyl, a is 1 or 2, b is an integer of 1 to 5, m, n and q are numbers in the range: 0≦m<1.0, 0<n<1.0, and 0.08≦q<0.5.

13. The composition of claim 12 wherein q is a number in the range of 0.1≦q<0.5.

14. A chemically amplified positive resist composition comprising a polymer comprising repeat units having the general formula (5′) or (6′):

wherein

denotes a substituted or unsubstituted aromatic hydrocarbon group, R 1 is each independently hydrogen, methyl or trifluoromethyl, R 2 is a straight, branched or cyclic C 1 -C 12 alkyl or aromatic hydrocarbon group, R 3 is a straight, branched or cyclic C 1 -C 12 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, wherein R 2 and R 3 , taken together, denote a C 5 -C 12 alkylene group, R 4 is hydrogen or methyl, R 5A is an acid labile group, a is 1 or 2, b and c each are an integer of 1 to 5, m1, m2, n and q are numbers in the range: 0<m1<1.0, 0<m2<1.0, 0<n<1.0, and 0.08≦q<0.5.

15. The composition of claim 14 wherein q is a number in the range of 0.1≦q<0.5.

16. A chemically amplified positive resist composition comprising a polymer being selected from the group consisting of the following formulae: