Resist composition and patterning process

1. A resist composition comprising a base polymer and a 2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane salt compound having the formula (A):

wherein R 1 to R 3 are each independently hydrogen, a C 1 -C 24 straight, branched or cyclic alkyl group, C 2 -C 24 straight, branched or cyclic alkenyl group, C 2 -C 24 straight, branched or cyclic alkynyl group, or C 6 -C 20 aryl group,

A − is an anion selected from the group consisting of hydroxide, chloride, bromide, iodide, nitrate, nitrite, chlorate, chlorite, perchlorate, hydrogencarbonate, dihydrogenphosphate, hydrogensulfate, thiocyanate, hydrogenoxalate, cyanide, iodate ions, and anions of the formulae (M-1) and (M-2):

wherein R 4 is hydrogen, or a C 1 -C 30 straight, branched or cyclic alkyl group, C 2 -C 30 straight, branched or cyclic alkenyl group, C 2 -C 30 straight, branched or cyclic alkynyl group, C 6 -C 20 aryl group, C 7 -C 20 aralkyl group, or C 3 -C 20 aromatic or aliphatic heterocycle-containing group, which may contain an ester, ether, sulfide, sulfoxide, carbonate, carbamate, sulfone, halogen, amino, amide, hydroxy, thiol or nitro moiety, with the proviso that R 4 does not contain a group of the formula (A)-1:

wherein Ar is a C 6 -C 16 aromatic group, R 7 and R 8 are each independently hydrogen, hydroxy, alkoxy, C 1 -C 6 straight, branched or cyclic alkyl group, or C 6 -C 10 aryl group, R 5 is fluorine, or a C 1 -C 10 straight, branched or cyclic fluoroalkyl group or fluorophenyl group, which may contain a hydroxy, ether, ester or alkoxy moiety, R 6 is hydrogen, or a C 1 -C 10 straight, branched or cyclic alkyl group, C 2 -C 10 straight, branched or cyclic alkenyl group, C 2 -C 10 straight or branched alkynyl group, or C 6 -C 10 aryl group, which may contain a hydroxy, ether, ester or alkoxy moiety.

2. The resist composition of claim 1 , further comprising an acid generator capable of generating sulfonic acid, sulfonimide or sulfonmethide.

3. The resist composition of claim 1 , further comprising an organic solvent.

4. The resist composition of claim 1 wherein the base polymer comprises recurring units having the formula (a1) or recurring units having the formula (a2):

wherein R 31 and R 33 are each independently hydrogen or methyl, R 32 and R 34 are each independently an acid labile group, X is a single bond, ester group, phenylene group, naphthylene group or a C 1 -C 12 linking group containing lactone ring, and Y is a single bond or ester group.

5. The resist composition of claim 4 , further comprising a dissolution inhibitor.

6. The resist composition of claim 4 which is a chemically amplified positive resist composition.

7. The resist composition of claim 1 wherein the base polymer is free of an acid labile group.

8. The resist composition of claim 7 , further comprising a crosslinker.

9. The resist composition of claim 7 which is a chemically amplified negative resist composition.

10. The resist composition of claim 1 wherein the base polymer comprises recurring units of at least one type selected from the formulae (f1) to (f3):

wherein R 51 , R 55 and R 59 each are hydrogen or methyl,

R 52 is a single bond, phenylene, —O—R 63 —, or —C(═O)—Y 1 —R 63 —, Y 1 is —O— or —NH—, R 63 is a C 1 -C 6 straight, branched or cyclic alkylene or alkenylene group which may contain a carbonyl, ester, ether or hydroxyl moiety, or phenylene group,

R 53 , R 54 , R 56 , R 57 , R 58 , R 60 , R 61 , and R 62 are each independently a C 1 -C 12 straight, branched or cyclic alkyl group which may contain a carbonyl, ester or ether moiety, or a C 6 -C 12 aryl group, C 7 -C 20 aralkyl group or mercaptophenyl group,

A 1 is a single bond, —A 0 —C(═O)—O—, —A 0 —O— or —A 0 —O—C(═O)—, A 0 is a C 1 -C 12 straight, branched or cyclic alkylene group which may contain a carbonyl, ester or ether moiety,

A 2 is hydrogen or trifluoromethyl,

Z 1 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, —O—R 64 —, or —C(═O)—Z 2 —R 64 —, Z 2 is —O— or —NH—, R 64 is a C 1 -C 6 straight, branched or cyclic alkylene or alkenylene group which may contain a carbonyl, ester, ether or hydroxyl moiety, or phenylene, fluorinated phenylene or trifluoromethyl-substituted phenylene group,

M − is a non-nucleophilic counter ion, and f1, f2 and f3 are numbers in the range: 0≦f1≦0.5, 0≦f2≦0.5, 0≦f3≦0.5, and 0<f1+f2+f3≦0.5.

11. The resist composition of claim 1 , further comprising a surfactant.

12. A process for forming a pattern comprising the steps of applying the resist composition of claim 1 onto a substrate, baking to form a resist film, exposing the resist film to high-energy radiation, and developing the exposed film in a developer.

13. The process of claim 12 wherein the high-energy radiation is ArF excimer laser radiation of wavelength 193 nm or KrF excimer laser radiation of wavelength 248 nm.

14. The process of claim 12 wherein the high-energy radiation is electron beam or extreme ultraviolet radiation of wavelength 3 to 15 nm.