Polymer, resist composition, and patterning process
To a resist composition, an alkali-soluble polymer having fluorinated ester-containing lactone units incorporated therein is included as an additive. The resist composition forms a resist film having a reduced contact angle after development. The resist film prevents water penetration during immersion lithography.
1. A polymer comprising recurring units having the general formulae (1a), (1b), and (1c):
wherein R 1a , R 1b and R 1c are each independently hydrogen, fluorine or a straight or branched C 1 -C 4 alkyl or fluoroalkyl group, R 2a is hydrogen, —R 3 —CO 2 R 7 , or —R 3 —OR 7 , R 2c is a straight, branched or cyclic C 2 -C 20 fluoroalkyl group, R 3 is a divalent organic group which may contain fluorine, R 4 is a methylene group or oxygen atom, R 5 is hydrogen, methyl or trifluoromethyl, R 6 is a straight, branched or cyclic C 2 -C 20 fluoroalkyl group, R 7 is hydrogen, a straight, branched or cyclic C 1 -C 20 alkyl or fluoroalkyl group, acid labile group or adhesive group, the subscripts “a,” “b” and “c” are numbers satisfying 0≦a<1, 0<b<1, 0≦c<1, and 0<a+b+c≦1,
said polymer having a weight average molecular weight of 1,000 to 500,000.
2. The polymer of claim 1 comprising recurring units having the general formulae (1a), (1b), and (1c):
wherein R 1a , R 1b and R 1c are each independently hydrogen, fluorine or a straight or branched C 1 -C 4 alkyl or fluoroalkyl group, R 2a is hydrogen, —R 3 —CO 2 H, or —R 3 —OH, R 2c is a straight, branched or cyclic C 2 -C 20 fluoroalkyl group, R 3 is a divalent organic group which may contain fluorine, R 4 is a methylene group or oxygen atom, R 5 is hydrogen, methyl or trifluoromethyl, R 6 is a straight, branched or cyclic C 2 -C 20 fluoroalkyl group, the subscripts “a,” “b” and “c” are numbers satisfying 0≦a<1, 0<b<1, 0≦c<1, and 0<a+b+c≦1,
said polymer having a weight average molecular weight of 1,000 to 500,000.
3. A resist composition comprising the polymer of claim 1 .
4. The resist composition of claim 3 , comprising
(A) a polymer which becomes soluble in an alkaline developer under the action of an acid,
(B) a compound which generates an acid upon exposure to high-energy radiation, and
(C) an organic solvent,
said resist composition being of chemically amplified positive type.
5. The resist composition of claim 4 , further comprising (D) a basic compound.
6. The resist composition of claim 4 , further comprising (E) a dissolution inhibitor.
7. A pattern forming process comprising the steps of:
(1) applying the resist composition of claim 3 onto a substrate to form a coating,
(2) heat treating the coating and exposing it to high-energy radiation through a photomask, and
(3) developing the exposed coating with a developer.
8. A pattern forming process comprising the steps of:
(1) applying the resist composition of claim 3 onto a substrate to form a photoresist film,
(2) forming a protective coating on the photoresist film,
(3) heat treating the coated substrate, and exposing it to high-energy radiation through a photomask while keeping water between a projection lens and the coated substrate, and
(4) stripping the protective coating and developing the resist film simultaneously using a developer.
9. The process of claim 7 , wherein an exposure light source emits high-energy radiation having a wavelength of 180 to 250 nm.
10. A pattern forming process comprising the steps of:
(1) applying the resist composition of claim 3 onto a mask blank substrate to form a coating,
(2) heat treating the coating and irradiating it in vacuum with an electron beam, and
(3) developing the coating with a developer.