Patterning process and resist composition

1. A pattern forming process comprising the steps of:

applying a resist composition onto a substrate, the resist composition comprising a polymer comprising recurring units having a hydroxyl group substituted with an acid labile group and an acid generator, or a polymer comprising recurring units having a hydroxyl group substituted with an acid labile group and recurring units capable of generating an acid upon exposure, a sulfonium or iodonium salt of perfluoroalkyl ether carboxylic acid, and an organic solvent,

prebaking the composition to form a resist film,

exposing the resist film to high-energy radiation,

baking, and

developing the exposed film in an organic solvent-based developer to form a negative pattern wherein the unexposed region of film is dissolved away and the exposed region of film is not dissolved,

wherein said sulfonium or iodonium salt of perfluoroalkyl ether carboxylic acid is a salt (Q1) or Q2) having the general formula (2):

wherein R 101a , R 101b and R 101c are each independently a straight, branched or cyclic C 1 -C 12 alkyl, alkenyl, oxoalkyl or oxoalkenyl group, C 6 -C 20 aryl group, or C 7 -C 12 aralkyl or aryloxoalkyl group, in which some or all hydrogen atoms may be substituted by ether, ester, carbonyl, carbonate, hydroxyl, carboxyl, halogen, cyano, amino, amide, nitro, sultone, sulfonic acid ester, sulfone groups, or substituent groups having sulfonium salt, or R 101b and R 101c may bond together to form a ring with the sulfur atom to which they are attached, R 101b and R 101c each are a C 1 -C 6 alkylene group when they form a ring,

R 101d and R 101e each are a C 6 -C 20 aryl group which may contain a straight, branched or cyclic C 1 -C 6 alkyl or alkoxy radical, or R 101d and R 101e may bond together to form a ring with the iodine atom to which they are attached, and

R 14 —COO − is selected from the group consisting of the following formulae:

2. The process of claim 1 wherein said polymer comprising recurring units having a hydroxyl group substituted with an acid labile group comprises recurring units of at least one type selected from recurring units (a1) to (a4) represented by the general formula (1):

wherein R 1 and R 4 are each independently hydrogen or methyl,

R 2 is a di- to pentavalent, straight, branched or cyclic C 1 -C 16 aliphatic hydrocarbon group which may contain an ether or ester radical,

R 3 and R 5 each are an acid labile group,

R 6 to R 9 and R 10 to R 13 are each independently hydrogen, cyano, a straight, branched or cyclic C 1 -C 6 alkyl group, organoxycarbonyl, or a group having an ether group or lactone ring, at least one of R 6 to R 9 and R 10 to R 13 has a hydroxyl group substituted with an acid labile group,

m is an integer of 1 to 4, n is 0 or 1, a1, a2, a3 and a4 are numbers in the range: 0≦a1<1.0, 0≦a2<1.0, 0≦a3<1.0, 0≦a4<1.0, and 0<a1+a2+a3+a4<1.0.

3. The process of claim 1 wherein the developer comprises at least one organic solvent selected from the group consisting of 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, isoamyl acetate, butenyl acetate, phenyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate.

4. The process of claim 1 wherein the step of exposing the resist film to high-energy radiation includes ArF excimer laser immersion lithography of 193 nm wavelength, EUV lithography of 13.5 nm wavelength or EB lithography.

5. The process of claim 4 wherein the ArF immersion lithography of 193 nm wavelength uses a halftone phase shift mask bearing a dot shifter pattern, whereby a pattern of holes is formed at the dots after development.

6. The process of claim 1 wherein the exposure step uses halftone phase shift masks and includes two exposures of two intersecting sets of lines, whereby a pattern of holes is formed at the intersections between lines after development.

7. The process of claim 1 wherein the exposure step uses a halftone phase shift mask bearing lattice-like shifter gratings, whereby a pattern of holes is formed at the intersections of gratings after development.

8. A pattern forming process according to any one of claims 1 , 2 and 3 to 7 , the process comprising the steps of:

applying a resist composition onto a substrate,

prebaking the composition to form a resist film,

forming a protective film on the resist film,

exposing the resist film to high-energy radiation,

baking, and

applying an organic solvent-based developer to dissolve away the protective film and the unexposed region of the resist film for forming a negative pattern wherein the exposed region of film is not dissolved.

9. A negative pattern-forming resist composition comprising a polymer comprising recurring units having an acid labile group substituted thereon of at least one type selected from recurring units (a1) to (a4) represented by the following general formula (1), a sulfonium salt (Q1) or iodonium salt (Q2) of perfluoroalkyl ether carboxylic acid having the following general formula (2), and an organic solvent,

wherein R 1 and R 4 are each independently hydrogen or methyl; R 2 is a di- to pentavalent, straight, branched or cyclic C 1 -C 16 aliphatic hydrocarbon group which may contain an ether or ester radical; R 3 and R 5 each are an acid labile group; R 6 to R 9 and R 10 to R 13 are each independently hydrogen, cyano, a straight, branched or cyclic C 1 -C 6 alkyl group, organoxycarbonyl, or a group having an ether group or lactone ring, at least one of R 6 to R 9 and R 10 to R 13 has a hydroxyl group substituted with an acid labile group; m is an integer of 1 to 4, n is 0 or 1, a1, a2, a3 and a4 are numbers in the range: 0≦a1<1.0, 0≦a2<1.0, 0≦a3<1.0, 0≦a4<1.0, and 0<a1+a2+a3+a4<1.0,

wherein R 101a , R 101b and R 101c are each independently a straight, branched or cyclic C 1 -C 12 alkyl, alkenyl, oxoalkyl or oxoalkenyl group, C 6 -C 20 aryl group, or C 7 -C 12 aralkyl or aryloxoalkyl group, in which some or all hydrogen atoms may be substituted by ether, ester, carbonyl, carbonate, hydroxyl, carboxyl, halogen, cyano, amino, amide, nitro, sultone, sulfonic acid ester, sulfone groups, or substituent groups having sulfonium salt, or R 101b and R 101c may bond together to form a ring with the sulfur atom to which they are attached, R 101b and R 101c each are a C 1 -C 6 alkylene group when they form a ring; R 101d and R 101e each are a C 6 -C 20 aryl group which may contain a straight, branched or cyclic C 1 -C 6 alkyl or alkoxy radical, or R 101d and R 101e may bond together to form a ring with the iodine atom to which they are attached; R 14 —COO − is selected from the group consisting of the following formulae:

said polymer being dissolvable in a developer selected from the group consisting of 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, isoamyl acetate, butenyl acetate, phenyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate.