Resist composition and patterning process
A resist composition comprises a base polymer which changes its alkali solubility under the action of an acid, and an additive copolymer comprising recurring units (a) and (b). R 1 is F or CF 3 , R 2 and R 3 are H or alkyl or form a ring, R 4 is H or an acid labile group, R 5 to R 6 are H, F, or alkyl, or two of R 5 to R 8 may together form a ring, m=0 or 1, 0.2≦a≦0.8, and 0.1≦b≦0.6. A resist film of the composition has good barrier property against water so that leaching of the resist film with water is controlled, minimizing a change of pattern profile due to leach-out.
1. A resist composition comprising
a polymer which changes its alkali solubility under the action of an acid as a base resin, and
a copolymer comprising recurring units (a) and (b) of the general formula (1) as an additive,
wherein R 1 is fluorine or trifluoromethyl, R 2 and R 3 are hydrogen or a straight, branched or cyclic C 1 -C 20 alkyl group, or R 2 and R 3 may bond together to form a ring with the carbon atom to which they are attached, and in this case, R 2 and R 3 together represent a straight, branched or cyclic C 2 -C 20 alkylene group, R 4 is hydrogen or an acid labile group,
R 5 to R 8 are independently selected from the group consisting of hydrogen, fluorine, and a straight, branched or cyclic C 1 -C 20 alkyl group, which may contain at least one ether or ester group, may be substituted with fluorine, and may contain a hydroxy group, or any two of R 5 to R 8 may bond together to form a ring with the carbon atom(s) to which they are attached, m is 0 or 1, a and b are numbers in the range: 0.2≦a≦0.8, and 0.1≦b≦0.6.
2. The resist composition of claim 1 which is a chemically amplified positive resist composition.
3. The resist composition of claim 2 , wherein the base resin is a polymer comprising recurring units having an acid labile group and recurring units having an adhesive group of hydroxy and/or lactone ring.
4. The resist composition of claim 1 which is a chemically amplified negative resist composition.
5. The resist composition of claim 1 , further comprising at least one member selected from the group consisting of an organic solvent, a basic compound, a dissolution regulator, a crosslinker, and a surfactant.
6. A pattern forming process comprising the steps of:
applying the resist composition of claim 1 onto a substrate to form a coating,
heat treating the coating and exposing it to high-energy radiation, and
developing the exposed coating with a developer.
7. The process of claim 6 , wherein the high-energy radiation has a wavelength of 180 to 250 nm.
8. The process of claim 6 , wherein the exposing step is by immersion lithography involving exposing the coating to high-energy radiation through a liquid.
9. The process of claim 8 , wherein the immersion lithography involves using high-energy radiation having a wavelength of 180 to 250 nm, introducing a liquid between the substrate having a resist coating formed thereon and a projection lens, and exposing the substrate to the high-energy radiation through the liquid.
10. The process of claim 8 , wherein the liquid is water.
11. The process of claim 6 , wherein the high-energy radiation is an electron beam.
12. The process of claim 11 , comprising the steps of:
applying the resist composition of claim 1 onto a mask blank substrate to form a coating,
heat treating the coating and exposing it to high-energy radiation, and
developing the exposed coating with a developer.