Resist underlayer film composition, method for producing polymer for resist underlayer film, and patterning process using the resist underlayer film composition

A method for producing a polymer for a resist underlayer film composition, wherein the polymer is obtained by condensing one or more kinds of a compound shown by the following general formula (1-1) with one or more kinds of a compound shown by the following general formula (2-3) and an equivalent body thereof to obtain a condensed body, which is then condensed with one or more kinds of a compound shown by the following general formula (2-1), a compound shown by the following general formula (2-2), and an equivalent body thereof,

• wherein each of R1 to R4 independently represents any of a hydrogen atom, a halogen atom, a hydroxyl group, an isocyanato group, a glycidyloxy group, a carboxyl group, an amino group, an alkoxyl group having 1 to 30 carbon atoms, an alkoxycarbonyl group having 1 to 30 carbon atoms, and an alkanoyloxy group having 1 to 30 carbon atoms, or an optionally substituted, saturated or unsaturated, organic group having 1 to 30 carbon atoms, wherein two substituents arbitrarily selected from each of R1 to R4 within a molecule may be bonded to form a cyclic substituent group:
• in the general formulae (2-1) and (2-2), Q represents an optionally substituted organic group having 1 to 30 carbon atoms, wherein two groups represented by Q arbitrarily selected within a molecule may be bonded to form a cyclic substituent group;
• n1 to n6 represent numbers of each substituent groups, while each of them represents an integer of 0 to 2:
• in the general formula (2-2), these numbers satisfy the relationships of 0≦n3+n5≦3, 0≦n4+n6≦4, and 0≦n3+n4≦4:
• and in the general formula (2-3), Y represents a hydrogen atom or an optionally substituted monovalent organic group having 1 to 30 carbon atoms, wherein (2-3) is different from (2-1) and (2-2).