Resist polymer, resist composition, process for pattern formation, and starting compounds for production of the resist polymer

1. A resist polymer comprising, as a structural unit, an acid-decomposable unit having a structure represented by formula (2):

wherein

K 1 and K 2 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene, arylene, a divalent thiazoline ring, a divalent oxazoline ring and a divalent imidazoline ring;

L 1 and L 2 each independently represent at least one selected from the group consisting of —C(O)O—, —C(O)— and —OC(O)—;

M 1 , M 2 and M 3 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene and arylene;

Y 1 and Y 2 each independently represent an acid-decomposable linkage;

k1, k2, l1, l2, m1, m2, m3 and n1 each represent the number of K 1 , K 2 , L 1 , L 2 , M 1 , M 2 , M 3 and Y 2 , respectively, and are each independently 0 or 1;

R 1 represents a hydrogen atom or a methyl group; and

S represents a sulfur atom.

2. The resist polymer according to claim 1 , which is obtainable by polymerizing a monomer containing at least a monomer represented by formula (10):

wherein

K 1 and K 2 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene, arylene, a divalent thiazoline ring, a divalent oxazoline ring and a divalent imidazoline ring;

L 1 and L 2 each independently represent at least one selected from the group consisting of —C(O)O—, —C(O)— and —OC(O)—;

M 1 , M 2 and M 3 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene and arylene;

Y 1 and Y 2 each independently represent an acid-decomposable linkage;

k1, k2, l1, l2, m1, m2, m3 and n1 each represent the number of K 1 , K 2 , L′, L 2 , M 1 , M 2 , M 3 and Y 2 , respectively, and are each independently 0 or 1;

R 1 represents a hydrogen atom or a methyl group; and

S represents a sulfur atom.

3. A resist composition comprising a resist polymer according to claim 1 .

4. A patterning process, comprising:

applying a composition comprising a resist composition according to claim 3 and a photoacid generator on a substrate to form a coated product,

exposing the coated product to form an exposed product, and

developing said exposed product with a developer.

5. A resist polymer comprising, as a structural unit, an acid-decomposable unit having a structure represented by formula (4):

wherein

S represents a sulfur atom;

K 1 and K 2 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene, arylene, a divalent thiazoline ring, a divalent oxazoline ring and a divalent imidazoline ring;

L 1 and L 2 each independently represent at least one selected from the group consisting of —C(O)O—, —C(O)— and —OC(O)—;

M 1 , M 2 and M 3 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene and arylene;

Y 1 and Y 2 each independently represent an acid-decomposable linkage; and

k1, k2, l1, l2, m1, m2, m3 and n1 each represent the number of K 1 , K 2 , L 1 , L 2 , M 1 , M 2 , M 3 and Y 2 , respectively, and are each independently 0 or 1.

6. The resist polymer according to claim 5 , which is obtainable by conducting polymerization using a polymerization initiator and a compound represented by formula (7):

wherein

S represents a sulfur atom;

K 1 and K 2 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene, arylene, a divalent thiazoline ring, a divalent oxazoline ring and a divalent imidazoline ring;

L 1 and L 2 each independently represent at least one selected from the group consisting of —C(O)O—, —C(O)— and —OC(O)—;

M 1 , M 2 and M 3 each independently represent at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene and arylene;

Y 1 and Y 2 each independently represent an acid-decomposable linkage; and

k1, k2, l1, l2, m1, m2, m3 and n1 each represent the number of K 1 , K 2 , L 1 , L 2 , M 1 , M 2 , M 3 and Y 2 , respectively, and are each independently 0 or 1.

7. The resist polymer according to claim 6 , wherein the compound represented by formula (7) is obtainable by a method comprising adding a compound represented by formula (15) to a compound represented by formula (14) to form a compound represented by formula (16) followed by dithiolation of the same:

wherein M 2 represents alkylene, cycloalkylene, oxyalkylene or arylene; m2 represents 0 or 1; R 10 and R 11 each independently represent a linear, branched or cyclic alkyl or alkenyl group having 1 to 18 carbon atoms or an aryl group; R 12 and R 13 each independently represent a hydrogen atom or a methyl group; S represents a sulfur atom; and Z represents an acyl group or an alkali metal.

8. The resist polymer according to claim 6 , wherein the compound represented by formula (7) is obtainable by a method comprising coupling of a diol represented by formula (17) with a carboxylic acid chloride having a sulfur atom represented by formula (18) to obtain a compound represented by formula (19) followed by dithiolation of the same:

wherein M 2 represents alkylene, cycloalkylene, oxyalkylene or arylene; m2 represents 0 or 1; R 10 and R 11 each independently represent a linear, branched or cyclic alkyl or alkenyl group having 1 to 18 carbon atoms or an aryl group; Cl represents a chlorine atom; S represents a sulfur atom; Z 2 represents an acyl group; and K 1 represents at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene, arylene, a divalent thiazoline ring, a divalent oxazoline ring and a divalent imidazoline ring.

9. The resist polymer according to claim 6 , wherein the compound represented by formula (7) is obtainable by a method comprising adding a carboxylic acid having a sulfur atom represented by formula (21) to a vinyl ether represented by formula (20) to obtain a compound represented by formula (22) followed by dithiolation of the same:

wherein M 2 represents alkylene, cycloalkylene, oxyalkylene or arylene; m2 represents 0 or 1; S represents a sulfur atom; Z 2 represents an acyl group; and K 1 represents at least one selected from the group consisting of alkylene, cycloalkylene, oxyalkylene, arylene, a divalent thiazoline ring, a divalent oxazoline ring and a divalent imidazoline ring.

10. A resist composition comprising a resist polymer according to claim 5 .

11. A patterning process comprising:

applying a composition comprising a resist composition according to claim 10 and a photoacid generator on a substrate to form a coated product,

exposing the coated product to form an exposed product, and

developing said exposed product with a developer.

12. A resist polymer which is obtainable by reacting a polymer precursor (P) having, on at least one molecular chain terminal thereof, at least one structure represented by formulas (8-1) to (8-4):

—B 1 —COOH  (8-1)

—S—B 1 —COOH  (8-2)

—O—B 1 —COOH  (8-3)

—NB 2 —B 1 —COOH  (8-4)

wherein

B 1 represents a linear, branched or cyclic divalent hydrocarbon group having 1 to 20 carbons which may have at least one group selected from the group consisting of a carboxyl group esterified with an alcohol having 1 to 6 carbon atoms, a cyano group and an amino group; and

B 2 represents a hydrogen atom, a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms

with a vinyl ether compound represented by formula (9):

wherein

n represents an integer of 2 to 24;

J represents a single bond or a divalent hydrocarbon group which may have at least one of a substituent and a heteroatom when n=2 or represents an n-valent hydrocarbon group which may have at least one of a substituent and a heteroatom when n≧3;

X represents a single bond or —B—B 11 —, —S—B 11 —, —O—B 11 —, —O—NB 12 —, —NB 12 —B 11 — or —O—Si(B 13 )(B 14 )—, wherein B 11 represents a linear, branched or cyclic divalent hydrocarbon group having 1 to 20 carbon atoms which may have at least one group selected from the group consisting of a carboxyl group esterified with an alcohol having 1 to 6 carbon atoms, a cyano group and an amino group, and the B 11 may have a heteroatom on the main skeleton thereof; B 12 represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms; and B 13 and B 14 each independently represent a hydrogen atom, a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms, and

wherein the polymer precursor (P) is obtainable by copolymerizing a monomer composition comprising at least one monomer containing an acid-eliminable group, at least one monomer containing a lactone skeleton and at least one monomer containing an alicyclic structure having a hydrophilic group in the presence of a polymerization initiator having a molecular chain terminal represented by formula (8-1) to (8-4), and

the resist polymer has two acetal groups within a main chain thereof.

13. A resist composition comprising a resist polymer according to claim 12 .

14. A patterning process comprising:

applying a composition comprising a resist composition according to claim 13 and a photoacid generator on a substrate to form a coated product,

exposing the coated product to form an exposed product, and

developing said exposed product with a developer.