Resist underlayer film-forming composition containing amide solvent

A resist underlayer film formed by coating a resist underlayer film-forming composition on a semiconductor stepped substrate comprised of a patterned portion including a pattern and an unpatterned portion without a pattern, the unpatterned portion having a lesser thickness to thereby create a step, and wherein an iso-dense bias (difference in film thickness of the coating above the patterned portion and film thickness above the unpatterned portion) is from 3 to 50 nm;

• the resist underlayer film-forming composition comprising a polymer and a compound represented by Formula (1) as a solvent:
• wherein, R1, R2, and R3 in Formula (1) each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, optionally interrupted by an oxygen atom, a sulfur atom, or an amide bond, and R1, R2, and R3 are the same or different and are optionally bonded to each other to form a ring structure,
• wherein the composition contains from 5% by weight to 30% by weight of the compound represented by Formula (1) relative to a total weight of the composition, and
• wherein the composition passes through a microfilter having a pore diameter of 0.1 μm;
• and
• wherein the polymer contains a structural unit represented by Formula (2):
• wherein, in Formula (2), A represents a divalent group derived from an aromatic compound selected from the group consisting of pyridine, phenylindole, phenylnaphthylamine, diphenylamine, hydroxydiphenylamine, carbazole, N,N′-diphenylethylenediamine and N,N′-diphenyl-1,4-phenylenediamine, in which a hydrogen atom of the aromatic compound is optionally replaced with an alkyl group having 1 to 20 carbon atoms, a condensed ring group, a heterocyclic group, a hydroxy group, an amino group, an ether group, an alkoxy group, a cyano group, a nitro group, or a carboxyl group;
• B1 and B2 are each selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, optionally interrupted by an oxygen atom or a sulfur atom, a heterocyclic group and an aryl group having 6 to 40 carbon atoms, of which a hydrogen atom is optionally substituted, and B1 and B2 optionally form a ring together with a carbon atom to which B1 and B2 are bonded.

A resist underlayer film-forming composition comprising a polymer and 3-methoxy-N,N-dimethylpropionamide,

• wherein the polymer contains a structural unit represented by Formula (2):
• wherein, in Formula (2), A represents a divalent group derived from an aromatic compound selected from the group consisting of pyridine, phenylindole, phenylnaphthylamine, diphenylamine, hydroxydiphenylamine, carbazole, N,N′-diphenylethylenediamine and N,N′-diphenyl-1,4-phenylenediamine, in which a hydrogen atom of the aromatic compound is optionally replaced with an alkyl group having 1 to 20 carbon atoms, a condensed ring group, a heterocyclic group, a hydroxy group, an amino group, an ether group, an alkoxy group, a cyano group, a nitro group, or a carboxyl group;
• B1 and B2 are each selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, optionally interrupted by an oxygen atom or a sulfur atom, a heterocyclic group and an aryl group having 6 to 40 carbon atoms, of which a hydrogen atom is optionally substituted, and B1 and B2 optionally form a ring together with a carbon atom to which B1 and B2 are bonded,
• wherein the composition contains from 5% by weight to 30% by weight of the 3-methoxy-N,N-dimethylpropionamide relative to a total weight of the composition, and
• wherein the composition passes through a microfilter having a pore diameter of 0.1 μM.