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, subs tituted norbornene polymer containing triethoxysilyl groups (NB), to the MS Q. The silsesquioxane-NB polymer film mixture was thermally cured followed by decomposition of the NB at temperatures above 400 degrees C. The dielect ric constant of the MSQ was lowered from 2.7 to 2.3 by creating 70 nm pores in the MSQ. The voids created in the MSQ exhibited a closed- pore structur e. 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-gla ss and its dielectric constant was lowered from 3.1 to 2.7. Infrared spectr oscopy was used to follow the curing of the MSQ and decomposition of the NB . (C) 1999 The Electrochemical Society. S1099- 0062( 98) 09- 026- 9. All ri ghts reserved.