Patent ID: 7820242

Claim:
A method, comprising: forming a precursor layer on a substrate, said precursor layer including a resin, polymeric nano-particles dispersed in said resin, and a solvent, each said polymeric nano-particle comprising a multi-arm core polymer and pendent polymers attached to said multi-arm core polymer, said multi-arm core polymer immiscible with said resin and said pendent polymers miscible with said resin; heating said precursor layer to a first temperature, said first temperature high enough to drive said solvent out of said precursor layer without decomposing more than about 0.5% said polymeric nano-particles, to form a pre-baked precursor layer; heating said pre-baked precursor layer to a second temperature, said second temperature high enough to cross-link at least about 90% of said resin without decomposing more than about 5% of said polymeric nano-particles, thereby converting said pre-baked precursor layer to a dielectric layer, said second temperature higher than said first temperature; and heating said dielectric layer to a third temperature, said third temperature high enough to thermally decompose at least about 99.5% of said polymeric nano-particles into decomposition products and to drive said decomposition products out of said dielectric layer, thereby creating voids in said dielectric layer and converting said dielectric layer to a porous dielectric layer, said third temperature higher than said second temperature.