Photosensitive siloxane composition and pattern forming method using the same

A photosensitive siloxane composition comprising:

• a polysiloxane (Pa)
• which contains a repeating unit represented by the following formula (ia):
• wherein
• R is hydrogen, a monovalent to trivalent, linear, branched or cyclic, saturated or unsaturated C1-30 aliphatic hydrocarbon group, or a monovalent to trivalent C6-30 aromatic hydrocarbon group, in said aliphatic hydrocarbon group and said aromatic hydrocarbon group, one or more methylene are unsubstituted or substituted with oxy, imide or carbonyl, one or more hydrogens are unsubstituted or substituted with fluorine, hydroxy or alkoxy, or one or more carbons are unsubstituted or substituted with silicon,
• when R is divalent or trivalent, R connects Si atoms contained in a plurality of repeating units, and all or part of said repeating units form a structure represented by the following formula (ia′):
• wherein
• L is —(CR′2)n— or
• provided that
• n is an integer of 1 to 3, and
• each R′ is independently hydrogen, methyl or ethyl;
• a photoactive agent;
• and
• a solvent.