Additive and resist underlayer film-forming composition containing the same
An additive for a resist underlayer film-forming composition containing a copolymer having structural units of Formulae (1) to (4), and a resist underlayer film-forming composition containing the additive: (where each R 1 is independently a hydrogen atom or methyl group, Ar is arylene group, Pr is a protecting group or a hydrogen atom, X is a direct bond or a —C(═O)O—R 2 — group, R 2 constituting the —C(═O)O—R 2 — group is a C 1-3 alkylene group, the alkylene group is bonded to a sulfur atom, R 3 is a hydrogen atom, methyl group, methoxy group, or halogeno group, R 4 is a C 1-3 alkyl group in which at least one hydrogen atom is substituted with a fluoro group, and Z is an organic group having 4 to 7-membered ring lactone skeleton, adamantane skeleton, or norbornane skeleton).
1. An additive for a resist underlayer film-forming composition comprising a copolymer having structural units of Formulae (1) to (4):
where
each R 1 is independently a hydrogen atom or methyl group,
Ar is arylene group,
Pr is a hydrogen atom or a protecting group selected from an acetyl group, a methoxymethyl group, an ethoxyethyl group, a C 4-8 tertiary alkyl group, or a pivaloyl group,
X is a direct bond or a —C(═O)O—R 2 — group,
R 2 constituting the —C(═O)O—R 2 — group is a C 1-3 alkylene group, the alkylene group is bonded to a sulfur atom,
R 3 is a hydrogen atom, methyl group, methoxy group, or halogeno group,
R 4 is a C 1-3 alkyl group in which at least one hydrogen atom is substituted with a fluoro group, and
Z is an organic group having 4 to 7-membered ring lactone skeleton, adamantane skeleton, or norbornane skeleton.
2. The additive according to claim 1 , wherein in the structural unit of Formula (1), Pr is the protecting group selected from an acetyl group, a methoxymethyl group, an ethoxyethyl group, a C 4-8 tertiary alkyl group, or a pivaloyl group.
3. The additive according to claim 1 , wherein the structural unit of Formula (2) is a structural unit of Formula (2a) or Formula (2b):
where
R 1 , R 2 , and R 3 each have the same definition as in claim 1 .
4. The additive according to claim 1 , wherein the structural unit of Formula (4) is a structural unit of Formula (4a):
where
each R 1 is independently a hydrogen atom or methyl group, and
R 5 is a C 2-5 hydrocarbon group.
5. The additive according to claim 1 , wherein
the copolymer is a compound synthesized by copolymerization of a monomer forming the structural unit of Formula (1), a monomer forming the structural unit of Formula (2), a monomer forming the structural unit of Formula (3), and a monomer forming the structural unit of Formula (4), and
the content of the monomer forming the structural unit of Formula (2) is 5% by mole to 40% by mole relative to a total of the four monomers of 100% by mole.
6. The additive according to claim 1 , wherein the copolymer has a weight average molecular weight of 3,000 to 20,000.
7. A resist underlayer film-forming composition containing
the additive according to claim 1 ,
a resin different from the copolymer,
an organic acid,
a cross-linking agent, and
a solvent.
8. The resist underlayer film-forming composition according to claim 7 , wherein the resin is polyester.
9. The resist underlayer film-forming composition according to claim 7 , wherein
the additive is contained in an amount of 5 parts by mass to 20 parts by mass relative to 100 parts by mass of the resin.
10. A method for forming a resist pattern comprising the steps of:
forming a resist underlayer film on a substrate using the resist underlayer film-forming composition according to claim 7 ;
forming a resist film on the resist underlayer film using a positive resist solution;
exposing the resist film through a photomask; and
developing the resist film by a solvent capable of dissolving an unexposed area of the resist film after the exposure, to remove the unexposed area.