Polymer, photoresist compositions including the same, and pattern formation methods

A polymer, comprising:

• a first repeating unit comprising a sulfone group, wherein the sulfone group is directly bonded to a group of formula —C(Ra)(Rb)—;
• and
• a second repeating unit comprising an acid labile group chosen from tertiary alkyl ester groups, secondary or tertiary aryl ester groups, secondary or tertiary ester groups having a combination of alkyl and aryl groups, tertiary alkoxy groups, acetal groups, ketal groups, tertiary carbonate groups, and tertiary carbamate groups, a base-decomposable group, a hydroxy aryl, or a combination thereof,
• wherein Ra and Rb are each independently hydrogen, halogen, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C3-30 heterocycloalkyl, substituted or unsubstituted C2-30 alkenyl, substituted or unsubstituted C3-30 cycloalkenyl, substituted or unsubstituted C3-30 heterocycloalkenyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C2-30 heteroaryl, substituted or unsubstituted C3-30 heteroarylalkyl, or substituted or unsubstituted C3-30 alkylheteroaryl,
• provided that at least one of Ra and Rb is hydrogen,
• wherein the first repeating unit is derived from a first monomer represented by Formula (1):
• wherein, in Formula (1),
• Xa is a polymerizable group comprising an ethylenically unsaturated carbon-carbon double bond;
• L1 is a single bond or a linking group;
• each L2 is independently a single bond, substituted or unsubstituted C1-30 alkyl, or substituted or unsubstituted C3-30 cycloalkyl;
• wherein at least one of L1 or L2 is not a single bond,
• each R1 is independently substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C3-30 heterocycloalkyl, substituted or unsubstituted C2-30 alkenyl, substituted or unsubstituted C3-30 cycloalkenyl, substituted or unsubstituted C3-30 heterocycloalkenyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C2-30 heteroaryl, substituted or unsubstituted C3-30 heteroarylalkyl, or substituted or unsubstituted C3-30 alkylheteroaryl;
• provided that at least one L2 or at least one R1 comprises the group of formula —C(Ra)(Rb)— that is directly bonded to —S(═O)2—;
• and
• n is an integer from 1 to 5.