Method for manufacturing semiconductor substrate, and resist underlayer film forming composition

A method for manufacturing a semiconductor substrate, the method comprising:

• applying a resist underlayer film forming composition directly or indirectly to a substrate to form a resist underlayer film;
• applying a composition for forming a resist film directly or indirectly to the resist underlayer film to form a resist film;
• exposing the resist film to light;
• and
• developing the exposed resist film,
• wherein
• the resist underlayer film forming composition comprises:
• a compound;
• and
• a solvent,
• wherein
• the compound comprises a plurality of groups each represented by —ORA, wherein each RA is independently a hydrogen atom, a monovalent heteroatom-containing group having 1 to 10 carbon atoms, or a monovalent organic group having 1 to 10 carbon atoms other than the monovalent heteroatom-containing group having 1 to 10 carbon atoms, wherein in the plurality of RA's, when a proportion of hydrogen atoms is denoted by x, a proportion of monovalent heteroatom-containing groups having 1 to 10 carbon atoms is denoted by y, and a proportion of monovalent organic groups having 1 to 10 carbon atoms is denoted by z, the compound satisfies relationships of x+y+z=100, 20≤x≤95, and 5≤y≤80, and
• the compound is a polymer comprising a repeating unit represented by formula (1), an aromatic ring-containing compound that has a molecular weight of 750 or more and 3000 or less and comprises —ORA, or a combination thereof:
• wherein in the formula (1), Ar1 is a divalent group comprising an aromatic ring having 5 to 40 ring members;
• R0 is a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms;
• R1 is a monovalent organic group having 1 to 40 carbon atoms;
• at least one selected from the group consisting of Ar1, R0 and R1 comprises —ORA.