Underlayer film-forming composition for use in forming a microphase-separated pattern

An underlayer film-forming composition for use in causing a layer comprising a block copolymer formed on a substrate to suffer phase separation,

• wherein the composition comprises a copolymer having:
• (A) a unit structure resulting from polymerizing a styrene compound containing a tert-butyl group,
• (B) a unit structure resulting from polymerizing an aromatic group-containing vinyl compound containing no hydroxy group, which differs from unit structure (A),
• (C) a unit structure resulting from polymerizing a compound containing (a)an (meth)acryloyl group and containing no hydroxy group, and
• (D) a unit structure resulting from polymerizing a crosslink-forming group-containing compound, wherein the crosslink-forming group is a hydroxy group, an epoxy group, a protected hydroxy group, or a protected carboxyl group,
• wherein the copolymer has a copolymerization ratio of:
• (A) 25 to 90% by mole, (B) more than 0 to 65% by mole, (C) 0 to 65% by mole, and (D) 10 to 20% by mole,
• wherein the copolymer in the composition has a proportion of an amount of unit structures containing an aromatic group based on a total amount of unit structures (A), (B), and (C) of 81 to 90% by mole, and
• wherein the unit structure (B) is represented by formula (4-1) or (4-2):
• wherein in formula (4-1), each of n quantity of Y independently represents an alkyl group, an alkoxy group, a cyano group, an amide group, an alkoxycarbonyl group, or a thioalkyl group, and n represents an integer of 1 to 5;
• wherein in formula (4-2), each of n quantity of Y independently represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, an amide group, an alkoxycarbonyl group, or a thioalkyl group, and n represents an integer of 0 to 7.