Resist underlayer composition and method of forming patterns using the composition

A resist underlayer composition, comprising:

• a polymer comprising a structural unit represented by Chemical Formula 1, a structural unit represented by Chemical Formula 2, or a combination thereof, a compound represented by Chemical Formula 3, and a solvent:
• wherein, in Chemical Formula 1 and Chemical Formula 2,
• A is a heterocyclic group including a nitrogen atom in a ring,
• L1 to L6 are each independently a single bond, a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C1 to C10 heteroalkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C2 to C20 heterocycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, a substituted or unsubstituted C1 to C20 heteroarylene group, or a combination thereof,
• X1 to X5 are each independently a single bond, —O—, —S—, —S(═O)—, —S(═O)2—, —C(═O)—, —(CO)O—, —O(CO)O—, —NRa— (wherein Ra is hydrogen, deuterium, or a C1 to C10 alkyl group), or a combination thereof,
• Y1 to Y3 are each independently a hydroxy group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, a substituted or unsubstituted C2 to C10 alkynyl group, a substituted or unsubstituted C1 to C10 heteroalkyl group, a substituted or unsubstituted C2 to C10 heteroalkenyl group, a substituted or unsubstituted C2 to C10 heteroalkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C2 to C20 heterocycloalkyl group, a substituted or unsubstituted C6 to C20 aryl group, a substituted or unsubstituted C3 to C20 heteroaryl group, or a combination thereof, and
• * is a linking point:
• (R1)x(R2)y(R3)Sn—(R4)(3-x-y) Chemical Formula 3
• wherein, in Chemical Formula 3,
• R1, R2, and R4 are each independently hydrogen, deuterium, a cyano group, an oxo group (═O), an azido group (—N3), a halogen atom, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C2 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C1 to C20 heteroalkyl group, a substituted or unsubstituted C2 to C20 heteroalkenyl group, a substituted or unsubstituted C2 to C20 heteroalkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C2 to C20 heterocycloalkyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C3 to C30 heteroaryl group, —ORb, —C(═O)Rc, —C(═O)ORd, —OC(═O)ORe, —NRfRg, —NRh(C═O)Ri (wherein Rb to Ri are each independently hydrogen, deuterium, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, a substituted or unsubstituted C2 to C10 alkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C1 to C10 heteroalkyl group, or a substituted or unsubstituted C6 to C30 aryl group), or a combination thereof,
• R3 is —ORj, —C(═O)Rk, —C(═O)ORl, —OC(═O)ORm, or -La-O—Rn (wherein La is a substituted or unsubstituted C1 to C5 alkylene group, or a substituted or unsubstituted C6 to C16 arylene group, and Rj to Rn are each independently hydrogen, deuterium, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, a substituted or unsubstituted C2 to C10 alkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C1 to C10 heteroalkyl group, or a substituted or unsubstituted C6 to C20 aryl group),
• x and y are each independently one selected from integers from 0 to 2, and 0≤x+y≤2.