Underlayer compositions and patterning methods

An underlayer composition, comprising a polymer comprising a repeating unit of formula (1):

• wherein,
• Ar is a monocyclic or polycyclic C5-60 aromatic group, wherein the aromatic group comprises one or more aromatic ring heteroatoms, a substituent group comprising a heteroatom, or a combination thereof;
• X is C or O;
• R1 is hydrogen, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 heteroalkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C2-30 heterocycloalkyl, substituted or unsubstituted C2-30 alkenyl, substituted or unsubstituted C2-30 alkynyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C3-30 heteroaryl, or substituted or unsubstituted C4-30 heteroarylalkyl;
• R2 is substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 heteroalkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C2-30 heterocycloalkyl, substituted or unsubstituted C2-30 alkenyl, substituted or unsubstituted C2-30 alkynyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C3-30 heteroaryl, substituted or unsubstituted C4-30 heteroarylalkyl, or —NR11R12, wherein R11 to R12 are each independently hydrogen, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C2-30 heterocycloalkyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C3-30 heteroaryl, or substituted or unsubstituted C4-30 heteroarylalkyl;
• optionally, R1 and R2 can be taken together form a 5- to 7-membered ring;
• optionally, one of R11 to R12 can be taken together with R1 to form a 5- to 7-membered ring;
• when X is C, Ra and Rb are each independently hydrogen, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 heteroalkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C2-30 heterocycloalkyl, substituted or unsubstituted C2-30 alkenyl, substituted or unsubstituted C2-30 alkynyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7_30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C3-30 heteroaryl, or substituted or unsubstituted C4-30 heteroarylalkyl;
• wherein Ra and Rb optionally may be taken together to form a 5- to 7-membered ring;
• wherein one of Ra or Rb optionally may be taken together with R2 to form a 5- to 7-membered ring;
• and
• when X is O, Ra and Rb are absent.