Low k, Porous Methyl Silsesquioxane and Spin-On-Glass

Low dielectric constant, porous silica was made from commercially available methyl silsesquioxane (MSQ) by the addition of a sacrificial polymer, substituted norbornene polymer containing triethoxysilyl groups (NB), to the MSQ. The silsesquioxane‐NB polymer film mixture was thermally cured followed by decomposition of the NB at temperatures above . The dielectric constant of the MSQ was lowered from 2.7 to 2.3 by creating pores in the MSQ. The voids created in the MSQ exhibited a closed‐pore structure. The concentration of NB in the MSQ affected the number of pores but not their size. Porous films were also created in a methyl siloxane spin‐on‐glass and its dielectric constant was lowered from 3.1 to 2.7. Infrared spectroscopy was used to follow the curing of the MSQ and decomposition of the NB.