Resist composition and patterning process

1. A chemically amplified resist composition comprising a polymer comprising recurring units (a1) of acid labile group-substituted (meth)acrylic acid, styrenecarboxylic acid or vinylnaphthalenecarboxylic acid, recurring units (a2) having an acid labile group-substituted phenolic hydroxyl group represented by the following formula (1) or both recurring units (a1) and recurring units (a2):

wherein R 1 and R 3 are each independently hydrogen or methyl, R 2 and R 4 each are an acid labile group, X 1 is a single bond, a C 1 -C 12 linking group having at least one of ester moiety, lactone ring, phenylene moiety or naphthylene moiety, a phenylene group, or a naphthylene group, X 2 is a single bond or an ester or amide group, a1 and a2 are numbers in the range: 0≦a1≦0.9, 0≦a2≦0.9, and 0≦a1+a2<1, and an acid generator,

said resist composition further comprising a metal salt selected from the group consisting of the following general formulae:

Cr 2+ (R 11 COO − ) 2

Cr 2+ R 12 (COO − ) 2

Cr 3+ (R 11 COO − ) 3

(Cr 3+ ) 2 (R 12 (COO − ) 2 ) 3

Cr 3 3+ (R 11 COO − ) 7 (OH) 2

(Cr 3+ ) 2 (R 13 COO − ) 6

Mn 2+ (R 11 COO − ) 2

Mn 2+ R 12 (COO − ) 2

Mn 3+ (R 11 COO − ) 3

(Mn 3+ ) 2 (R 12 (COO − ) 2 ) 3

Fe 2+ R 12 (COO − ) 2

Fe 3+ (R 11 COO − ) 3

(Fe 3+ ) 2 (R 12 (COO − ) 2 ) 3

Fe 3+ R 13 (COO − ) 3

Fe 2+ (R 11 COO − ) 2

Co 2+ (R 11 COO − ) 2

Co 2+ R 12 (COO − ) 2

Ni 2+ (R 11 COO − ) 2

Ni 2+ R 12 (COO − ) 2

Cu + R 11 COO −

(Cu + ) 2 R 12 (COO − ) 2

Cu 2+ (R 11 COO − ) 2

Cu 2+ R 12 (COO − ) 2

Zn + R 11 COO −

(Zn + ) 2 R 12 (COO − ) 2

Zn 2+ (R 11 COO − ) 2

Ag + R 11 COO −

(Ag + ) 2 R 12 (COO − ) 2

Cd 2+ (R 11 COO − ) 2

Cd 2+ R 12 (COO − ) 2

Sn 2+ (R 11 COO − ) 2

Sn 2+ R 12 (COO − ) 2

Sn 4+ (R 11 COO − ) 4

Sn 4+ (R 12 (COO − ) 2 ) 2

Sn 4+ R 14 (COO − ) 4

Sb 3+ (R 11 COO − ) 3

(Sb 3+ ) 2 (R 12 (COO − ) 2 ) 3

Sb 3+ R 11 (COO − ) 3

Hf 4+ (R 11 COO − ) 4

Hf 4+ (R 12 COO − ) 2 ) 2

Hf 4+ R 14 (COO − ) 4

wherein R 11 is each independently hydrogen, or a straight, branched or cyclic C 1 -C 20 alkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, or C 6 -C 20 aryl group which may have a hydroxyl, ether, ester, amino, amide, sulfonic acid ester, halogen, cyano, nitro, carbonate, carbamate, thiol, sulfide, thioketone radical or hetero-aromatic ring; R 12 is a single bond, or a straight, branched or cyclic C 1 -C 20 alkylene, alkenylene, alkynylene, or C 6 -C 20 arylene group which may have a hydroxyl, ether, ester, amino, amide, sulfonic acid ester, halogen, cyano, nitro, carbonate, carbamate, thiol, sulfide, thioketone radical or hetero-aromatic ring; R 13 and R 14 each are an alkylene, arylene, alkenylene or alkynylene group as defined for R 12 , in which one or two hydrogen atoms are substituted by one or two carboxyl groups,

said metal salt being present in an amount of 0.02 to 30 parts by weight per 100 parts by weight of the polymer.

2. The chemically amplified resist composition of claim 1 , wherein in addition to the recurring units (a1) and (a2), the copolymer comprises recurring units (b1), (b2) or (b3) of a sulfonium salt having the general formula (2):

wherein R 120 , R 124 , and R 128 each are hydrogen or methyl, R 121 is a single bond, phenylene, —O—R—, or —C(═O)—Y—R—, Y is oxygen or NH, R is a straight, branched or cyclic C 1 -C 6 alkylene group, C 3 -C 10 alkenylene or phenylene group, which may contain a carbonyl, ester, ether or hydroxyl moiety, R 122 , R 123 , R 125 , R 126 , R 127 , R 129 , R 130 , and R 131 are each independently a straight, branched or cyclic C 1 -C 12 alkyl group which may contain a carbonyl, ester or ether moiety, or a C 6 -C 12 aryl, C 7 -C 20 aralkyl, or thiophenyl group which may contain a straight, branched or cyclic C 1 -C 10 alkyl, halogen, trifluoromethyl, cyano, nitro, hydroxyl, alkoxy, alkoxycarbonyl or acyloxy radical, Z 1 is a single bond or —C(═O)—Z 3 —R 132 —, Z 2 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene —O—R 132 — or —C(═O)—Z 3 —R 132 , Z 3 is oxygen or NH, R 132 is a straight, branched or cyclic C 1 -C 6 alkylene group, alkenylene, or phenylene group, which may contain a carbonyl, ester, ether or hydroxyl moiety, a pair of R 122 and R 123 , R 125 and R 126 , R 125 and R 127 , R 126 and R 127 , R 129 and R 130 , R 129 and R 131 , or R 130 and R 131 may bond directly or via a methylene moiety or ether bond to form a ring with the sulfur atom, R 133 is hydrogen or trifluoromethyl, M − is a non-nucleophilic counter ion, b1, b2 and b3 are in the range of 0≦b1≦0.5, 0≦b2≦0.5, 0≦b3≦0.5, and 0≦b1+b2+b3≦0.5.

3. The chemically amplified resist composition of claim 1 , further comprising at least one component selected from the group consisting of an organic solvent, a dissolution inhibitor, an acid generator, a basic compound, and a surfactant.

4. The chemically amplified resist composition of claim 1 , wherein the metal salt is present in an amount of 0.55 to 20 parts by weight per 100 parts by weight of the polymer.

5. The chemically amplified resist composition of claim 1 , wherein said metal salt is selected from the group consisting of the following general formulae:

Cr 2+ (R 11 COO − ) 2

Cr 2+ R 12 (COO − ) 2

Cr 3+ (R 11 COO − ) 3

(Cr 3+ ) 2 (R 12 COO − ) 2 ) 3

Cr 3 3+ (R 11 COO − ) 7 (OH) 2

(Cr 3+ ) 2 (R 13 COO − ) 6

Mn 2+ (R 11 COO − ) 2

Mn 2+ R 12 (COO − ) 2

Mn 3+ (R 11 (COO − ) 3

(Mn 3+ ) 2 (R 12 (COO − ) 2 ) 3

Fe 2+ R 12 (COO − ) 2

Fe 3+ (R 11 COO − ) 3

(Fe 3+ ) 2 (R 12 (COO − ) 2 ) 3

Fe 3+ R 13 (COO − ) 3

Fe 2+ (R 11 COO − ) 2

Co 2+ (R 11 COO − ) 2

Co 2+ R 12 (COO − ) 2

Ni 2+ (R 11 COO − ) 2

Ni 2+ R 12 (COO − ) 2

Zn + R 11 COO −

(Zn + ) 2 R 12 (COO − ) 2

Zn 2+ (R 11 COO − ) 2

Ag + R 11 COO −

(Ag + ) 2 R 12 (COO − ) 2

Cd 2+ (R 11 COO − ) 2

Cd 2+ R 12 (COO − ) 2

Sn 2+ (R 11 COO − ) 2

Sn 2+ R 12 (COO − ) 2

Sn 4+ (R 11 COO − ) 4

Sn 4+ (R 12 (COO − ) 2 ) 2

Sn 4+ R 14 (COO − ) 4

Sb 3+ (R 11 COO − ) 3

(Sb 3+ ) 2 (R 12 (COO − ) 2 ) 3

Sb 3+ R 13 (COO − ) 3

Hf 4+ (R 11 COO − ) 4

Hf 4+ (R 12 (COO − ) 2 ) 2

Hf 4+ R 14 (COO − ) 4

wherein R 11 is each independently hydrogen, or a straight, branched or cyclic C 1 -C 20 alkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, or C 6 -C 20 aryl group which may have a hydroxyl, ether, ester, amino, amide, sulfonic acid ester, halogen, cyano, nitro, carbonate, carbamate, thiol, sulfide, thioketone radical or hetero-aromatic ring; R 12 is a single bond, or a straight, branched or cyclic C 1 -C 20 alkylene, alkenylene, alkynylene, or C 6 -C 20 arylene group which may have a hydroxyl, ether, ester, amino, amide, sulfonic acid ester, halogen, cyano, nitro, carbonate, carbamate, thiol, sulfide, thioketone radical or hetero-aromatic ring; R 13 and R 14 each are an alkylene, arylene, alkenylene or alkynylene group as defined for R 12 , in which one or two hydrogen atoms are substituted by one or two carboxyl groups.

6. A pattern forming process comprising the steps of coating the chemically amplified resist composition of claim 1 onto a substrate, baking, exposing to high-energy radiation, and developing with a developer.

7. The process of claim 6 wherein the high-energy radiation is EUV radiation having a wavelength of 3 to 15 nm.

8. The process of claim 6 wherein the high-energy radiation is an electron beam at an accelerating voltage of 1 to 150 keV.