Photoacid generators, chemically amplified resist compositions, and patterning process

1. A photoacid generator for use in chemically amplified resist compositions, having the general formula (1):

wherein R is independently selected from the class consisting of hydrogen, fluorine, chlorine atoms, nitro groups, and substituted or unsubstituted, straight, branched or cyclic alkyl and alkoxy groups of 1 to 12 carbon atoms, n is 0 or 1, m is 1 or 2, r is an integer of 0 to 4, and r′ is an integer of 0 to 5.

2. A photoacid generator for use in chemically amplified resist compositions, having the formula (1a):

3. A chemically amplified resist composition comprising

(A) a resin which changes its solubility in an alkaline developer under the action of an acid, and

(B) the photoacid generator of claim 1 .

4. A chemically amplified positive resist composition comprising

(A) a resin which changes its solubility in an alkaline developer under the action of an acid, and

(B) the photoacid generator of claim 1 .

5. The resist composition of claim 3 , further comprising (C) a compound capable of generating an acid upon exposure to radiation, other than component (B).

6. The resist composition of claim 3 wherein the resin (A) has such substituent groups having C—O—C linkages that the solubility in an alkaline developer changes as a result of scission of the C—O—C linkages under the action of an acid.

7. The resist composition of claim 6 wherein the resin (A) is a polymer containing phenolic hydroxyl groups in which hydrogen atoms of the phenolic hydroxyl groups are substituted with acid labile groups of one or more types in a proportion of more than 0 mol % to 80 mol % on the average of the entire hydrogen atoms of the phenolic hydroxyl groups, the polymer having a weight average molecular weight of 3,000 to 100,000.

8. The resist composition of claim 6 wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a):

wherein R 1 is hydrogen or methyl, R 2 is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, R 3 is an acid labile group, S and T are positive integers, satisfying 0<T/(S+T)≦0.8,

wherein the polymer contains units in which hydrogen atoms of phenolic hydroxyl groups are partially substituted with acid labile groups of one or more types, a proportion of the acid labile group-bearing units is on the average from more than 0 mol % to 80 mol % based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.

9. The resist composition of claim 6 wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a′):

wherein R 1 is hydrogen or methyl, R 2 is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R 3 is an acid labile group, R 3a is hydrogen or an acid labile group, at least some of R 3a being acid labile groups, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, M and N are positive integers, L is 0 or a positive integer, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦0.8,

wherein the polymer contains on the average from more than 0 mol % to 50 mol % of those units derived from acrylate and methacrylate, and also contains on the average from more than 0 mol % to 80 mol % of acid labile group-bearing units, based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.

10. The resist composition of claim 6 wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a″):

wherein R 1 is hydrogen or methyl, R 2 is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R 3 is an acid labile group, R 3a is hydrogen or an acid labile group, at least some of R 3a being acid labile groups, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, yy is 0 or a positive integer, satisfying x+yy≦4, A and B are positive integers, C, D and E each are 0 or a positive integer, satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and 0<(C+D+E)/(A+B+C+D+E)≦0.8,

wherein the polymer contains on the average from more than 0 mol % to 50 mol % of those units derived from indene and/or substituted indene, and also contains on the average from more than 0 mol % to 80 mol % of acid labile group-bearing units, based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.

11. The resist composition of claim 6 wherein the acid labile group is a tertiary alkyl group of 4 to 20 carbon atoms or a group of the following general formula (5):

wherein R 8 is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or an aryl group of 6 to 20 carbon atoms which may be substituted, h is 0 or 1, i is 0, 1, 2 or 3, satisfying 2h+i=2 or 3.

12. The resist composition of claim 3 , further comprising (D) a basic compound.

13. The resist composition of claim 3 , further comprising (E) an organic acid derivative.

14. The resist composition of claim 3 , further comprising (F) an organic solvent which is a propylene glycol alkyl ether acetate, an alkyl lactate or a mixture thereof.

15. A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of claim 3 onto a substrate to form a coating,

(ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask,

(iii) optionally heat treating the exposed coating, and developing the coating with a developer.

16. A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of claim 3 onto an inorganic substrate such as a SiON film to form a coating,

(ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask,

(iii) optionally heat treating the exposed coating, and developing the coating with a developer.

17. A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of claim 3 onto a substrate to form a coating,

(ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask,

(iii) optionally heat treating the exposed coating, and developing the coating with a developer to form a pattern profile, and

(iv) heat treating for causing the pattern profile to flow for thereby reducing its size.