Radiation-sensitive composition changing in refractive index and utilization thereof

A composition comprising:

• (A) a decomposable compound;
• (B) a hydrolyzate of at least one compound selected from the group consisting of an alkoxide represented by the following formula (1′):
• M(OR)mYn (1′)
• wherein M is a positive divalent to pentavalent atom, R is an alkyl group or aryl group, Y is a hydrogen atom, alkyl group, aryl group, hydroxyl group, alkoxyl group or aryloxy group, and m and n are each independently an integer of 0 or more, with the proviso that (m+n) is equal to the valence of M,
• and a halogen compound represented by the following formula (2′):
• MXmYn (2′)
• wherein M, Y, m and n are as defined in the above formula (1′), and X is a halogen atom;
• and
• (C) a radiation sensitive decomposer,
• wherein the radiation sensitive decomposer (C) comprises a radiation sensitive acid generator or a radiation sensitive base generator, and
• wherein the decomposable compound (A) comprises a polymer having at least one of structures represented by the following formulas (1) to (6) and (7) to (11):
• wherein R1 is an alkylene group, perfluoroalkylene group, alkylsilylene group, alkylene-arylene-alkylene group or arylene group, and R2 is an alkylene group, perfluoroalkylene group, alkylene-arylene-alkylene group, arylene group, alkylsilylene group or alkylgermylene group, with the proviso that the above alkylene group or perfluoroalylene group may contain a —O—, —CO—, —COO— or —OCOO— bond;
• wherein M is Si or Ge, R3 is an alkylene group, perfluoroalkylene group, alkylene-arylene-alkylene group, arylene group, alkylsilylene group, alkylgermylene group or single bond, R4 is an oxygen atom, alkylene group, perfluoroalkylene group, alkylene-arylene-alkylene group, arylene group, alkylsilylene group or single bond, R5, R6, R7 and R8 are each independently a hydrogen atom, alkyl group, aryl group, alkoxyl group, thioalkyl group, alkoxyester group, perfluoroalkyl group, perfluoroalkoxyl group, perfluoroalkoxyester group or perfluoroaryl group, and m is an integer of 0 to 2, with the proviso that the above alkylene group or perfluoroalkylene group may contain a —O—, —CO—, —COO— or —OCOO— bond;
• wherein R9 and R10 are each independently an alkylene group, perfluoroalkylene group, alkylene-arylene-alkylene group, arylene group, alkylsilylene group or alkylgermylene group, with the proviso that the above alkylene group or perfluoroalkylene group may contain a —O—, —CO—, —COO— or —OCOO— bond;
• wherein R11 is an oxyalkylene group or single bond, and R12 is a hydrogen atom, alkyl group, alkoxyl group, alkoxyester group, perfluoroalkyl group, perfluoroalkoxyester group, perfluoroaryl group, alkylene-arylene-alkylene group or aryl group;
• wherein R13 is a hydrogen atom, alkyl group, alkoxyl group, alkoxyester group, perfluoroalkyl group, perfluoroalkoxyl group, perfluoroalkoxyester group, perfluoroaryl group or aryl group;
• wherein R14 is an alkylene group or a structure represented by the following formula (6)-1, (6)-2 or (6)-3:
• wherein R15, R16, R17 and R18 are each independently a hydrogen atom, chain alkyl group having 1 to 6 carbon atoms, chlorine atom, bromine atom, iodine atom, hydroxyl group, mercapto group, carboxyl group, alkoxyl group having 1 to 6 carbon atoms, alkylthio group having 1 to 6 carbon atoms, haloalkyl group having 1 to 6 carbon atoms, haloalkoxyl group having 1 to 6 carbon atoms, haloalkylthio group having 1 to 6 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms, mercaptoalkyl group having 1 to 6 carbon atoms, hydroxyalkoxyl group having 1 to 6 carbon atoms, mercaptoalkylthio group having 1 to 6 carbon atoms, aryl group having 6 to 10 carbon atoms or aralkyl group having 7 to 11 carbon atoms,
• —O—R19—O— (6)-2
• wherein R19 is an alkylene group, and
• —NH—R20—NH— (6)-3
• wherein R20 is an alkylene group;
• wherein R21 is an alkylene group, alkylene-arylene-alkylene group or arylene group;
• wherein R22 is an alkylene group, aralkylene group or arylene group, R23 is an alkylene group, aralkylene group, arylene group, alkylene-arylene-alkylene group, alkylsilylene group or alkylgermylene group, R24, R25, R26 and R27 are each independently a hydrogen atom, alkyl group, aryl group, alkoxyl group or thioalkyl group, and i and j are each independently 0 or 1;
• wherein R28 is an alkylene group, aralkylene group or arylene group, and R29 is an alkylene group, aralkylene group, arylene group, alkylene-arylene-alkylene group, alkylsilylene group or alkylgermylene group;
• wherein R30 and R31 are each independently an alkylene group, aralkylene group, arylene group, alkylene-arylene-alkylene group, alkylsilylene group or alkylgermylene group;
• and
• wherein R32 and R33 are each independently an alkylene group, aralkylene group, arylene group, alkylene-arylene-alkylene group, alkylsilylene group or alkylgermylene group.