Resist underlayer composition, and method of forming patterns using the composition

A resist underlayer composition, comprising:

• a solvent;
• and
• a polymer that includes a structural unit represented by Chemical Formula 1 and a structural unit represented by Chemical Formula 2,
• wherein, in Chemical Formula 1,
• A is a substituted or unsubstituted C1 to C30 alkylene group, a substituted or unsubstituted C1 to C30 heteroalkylene group, a substituted or unsubstituted C3 to C30 cyclo alkylene group, a substituted or unsubstituted C2 to C30 heterocyclo alkylene group, a substituted or unsubstituted C6 to C30 arylene group, a substituted or unsubstituted C2 to C30 heteroarylene group, or a combination thereof,
• X is a group including an electrophile having, at a terminal end thereof, an epoxy group, a C1 to C6 alkoxy group, R—(C═O)—, in which R is hydrogen or a C1 to C10 alkyl group, R′O—(C═O)—, in which R′ is a C1 to C10 alkyl group, or a halogen,
• Y and Y′ are each independently a single bond, oxygen, carbonyl, —(CH2)O—, —(CH2)S—, —(CH2)NH—, or a combination thereof,
• R2 to R9 are independently hydrogen, a hydroxy group, a halogen, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C2 to C30 alkenyl group, a substituted or unsubstituted C2 to C30 alkynyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C1 to C30 heteroalkyl group, a substituted or unsubstituted C2 to C30 heteroaryl group, or a combination thereof,
• a, b, c, and d are independently an integer of 0 to 100, a sum of a and b being 1 to 99, and a sum of c and d being 1 to 99, and
• is a linking point,
• wherein, in Chemical Formula 2, R1 is a substituted or unsubstituted C1 to C30 alkylene group, a substituted or unsubstituted C1 to C30 heteroalkylene group, a substituted or unsubstituted C3 to C30 cycloalkylene group, a substituted or unsubstituted C6 to C30 arylene group, a substituted or unsubstituted C2 to C30 heteroarylene group, —((CmH2m)O)n—, in which m and n are each independently an integer of 1 to 10, or a combination thereof,
• E is a group including a nucleophile, and
• is a linking point.