Radiation-sensitive composition, pattern formation method, and photo-degradable base

A radiation-sensitive composition comprising:

• a polymer comprising an acid-releasable group;
• and a compound (Q) represented by formula (1):
• wherein L1 represents an ester group, —CO—NR3—, a (thio)ether group, or a sulfonyl group;
• when L1 is an ester group, a (thio)ether group, or a sulfonyl group, R1, R2, and R3 satisfy condition (i) or (ii);
• when L1 is —CO—NR3—, R1, R2, and R3 satisfy condition (i), (ii), or (iii);
• R4 represents a hydrogen atom, a substituted or unsubstituted C1 to C20 monovalent hydrocarbon group, a halogen atom, a hydroxy group, or a nitro group;
• R5 represents a C1 to C20 monovalent hydrocarbon group, a C1 to C20 monovalent halogenated hydrocarbon group, or a halogen atom, and optionally two R5s taken together represent an alicyclic structure together with the carbon atom(s) between the two R5s;
• L2 represents a single bond or a divalent linking group;
• each of n1 and n2 is independently an integer of 1 to 4;
• n3 is an integer of 0 to 5;
• when n3 is ≥2, a plurality of R5s are identical to or different from one another;
• and a plurality of R4s are identical to or different from one another:
• (i) R1 represents a C1 to C20 monovalent organic group which bound to L1 via a carbon atom included in R1;
• R2 represents a substituted or unsubstituted divalent hydrocarbon group, comprising no fluorine atom;
• and R3 represents a hydrogen atom or a monovalent hydrocarbon group;
• (ii) R1 and R2 taken together represent a group comprising an aliphatic heterocyclic structure together with L1 to which R1 and R2 are bound, provided that R2 comprises no fluorine atom;
• and R3 represents a hydrogen atom or a monovalent hydrocarbon group;
• and
• (iii) R1 represents a C1 to C20 monovalent organic group which bound to L1 via a carbon atom included in R1;
• R2 and R3 taken together represent an aliphatic heterocyclic structure together with L1 to which R2 and R3 are bound, the aliphatic heterocyclic structure comprising no fluorine atom.