Photo-patternable dielectric materials curable to porous dielectric materials, formulations, precursors and methods of use thereof

A method, comprising:

• (a) forming on a substrate, a layer of a photoactive formulation comprising:
• a photoacid generator;
• a casting solvent;
• and
• a silsesquioxane polymer, said silsesquioxane polymer being a terpolymer or a tetrapolymer, one monomer thereof being
• where R2 is an alkyl moiety containing 1 to 20 carbon atoms;
• (b) patternwise exposing said layer with light to generate an exposed layer;
• (c) baking said exposed layer to cross-link said silsesquioxane polymer in regions of said exposed layer exposed to said light to generate a baked layer;
• (d) developing said baked layer to remove portions of said baked layer not exposed to said light to form a first trench in a developed layer;
• (e) curing said developed layer to generate porosity in said silsesquioxane polymer and form a porous patterned cured layer including said first trench;
• and
• (f) filling said first trench in said porous patterned cured layer with an electrically conductive material.