Onium salt compound, polymer compound comprising the salt compound, chemically amplified resist composition comprising the polymer compound, and method for patterning using the composition

1. A polymer compound comprising a repeating unit represented by the following formula (5), a repeating unit represented by the following formula (6), and a repeating unit represented by the following formula (7):

wherein R 1 represents a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms; and A represents a group represented by the following formula (2) or formula (3):

wherein R 2 , R 3 , R 4 , R 5 and R 6 each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted allyl group having 3 to 10 carbon atoms, a substituted or unsubstituted perfluoroalkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted benzyl group, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms; and two or more of R 2 , R 3 and R 4 may be linked to each other to form a saturated or unsaturated carbon ring or a saturated or unsaturated heterocyclic ring;

wherein R 7 represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms which is substituted with a group selected from an ether group, an ester group, a carbonyl group, an acetal group, an epoxy group, a nitrile group and an aldehyde group; and R 8 represents a hydrogen atom, a methyl group, or a trifluoromethyl group;

wherein X represents one selected from olefin, vinyl, styrene, and derivatives thereof.

2. The polymer compound according to claim 1 , wherein the polymer compound comprises three different species of the repeating unit represented by formula (6).

3. The polymer compound according to claim 2 , wherein when the polymer compound comprising three different species of the repeating unit represented by formula (6) is represented by the following formula (8), the polymer compound is represented by any one of the formulas of formula (9):

wherein R 1 represents a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms; R 7a , R 7b and R 7c each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, or a linear or branched alkyl group having 1 to 30 carbon atoms which is substituted with an ether group, an ester group, a carbonyl group, an acetal group, an epoxy group, a nitrile group or an aldehyde group; R 8a , R 8b and R 8c each independently represent a hydrogen atom, a methyl group or a trifluoromethyl group; and A represents a group represented by the following formula (2) or formula (3):

wherein R 2 , R 3 , R 4 , R 5 and R 6 each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted allyl group having 3 to 10 carbon atoms, a substituted or unsubstituted perfluoroalkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted benzyl group, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms; and two or more of R 2 , R 3 and R 4 may be linked to each other to form a saturated or unsaturated carbon ring or a saturated or unsaturated heterocyclic ring;

4. The polymer compound according to claim 1 , wherein A is represented by one of the following formulas of formula (4):

5. The polymer compound according to claim 1 , further comprising a repeating unit having an acid-labile group, and a repeating unit having a hydroxyl group, a lactone ring group, or both a hydroxyl group and a lactone ring group.

6. A chemically amplified resist composition comprising the polymer compound according to claim 1 , an acid generator, additives, and a solvent.

7. The chemically amplified resist composition according to claim 6 , wherein the content of the moiety —(SO 3 ) − (A) + in the polymer compound is 0.5 parts by weight to 15 parts by weight based on 100 parts by weight of the total solid fraction of the chemically amplified resist composition.

8. The chemically amplified resist composition according to claim 6 , wherein the content of the polymer compound is 3% by weight or more based on the chemically amplified resist composition.

9. The chemically amplified resist composition according to claim 6 , wherein the content of the polymer compound is 5% by weight based on the chemically amplified resist composition.

10. A method for forming a pattern, the method comprising:

(a) applying the chemically amplified resist composition according to claim 6 on a substrate;

(b) heat treating the substrate coated with the chemically amplified resist composition, and then exposing the substrate with high energy radiation; and

(c) developing the outcome from the step (b) using a developer solution.

11. The method according to claim 10 , wherein the exposing the substrate with high energy radiation employs ultraviolet irradiation, X-ray irradiation, or an electron beam irradiation.

12. The method according to claim 10 , wherein the wavelength of the high energy radiation is in the range of 180 nm to 250 nm.

13. A chemically amplified resist composition comprising the polymer compound according to claim 2 , an acid generator, additives, and a solvent.

14. A chemically amplified resist composition comprising the polymer compound according to claim 3 , an acid generator, additives, and a solvent.

15. A chemically amplified resist composition comprising the polymer compound according to claim 4 , an acid generator, additives, and a solvent.

16. A chemically amplified resist composition comprising the polymer compound according to claim 5 , an acid generator, additives, and a solvent.