Repair of porous methylsilsesquioxane films using supercritical carbon dioxide

Porous methylsilsesquioxane (p-MSQ) films (JSR LKD 5109) were treated with alkyldimethyhnonochlorosilanes having chain lengths of one, four, and eight carbon atoms dissolved in supercritical. carbon dioxide at 150-300 arm and 50-60degreesC to repair oxygen ashing damage. Fourier transform infrared (FTIR) spectroscopy showed that trimethylchlorosilane (TMCS), butyldimethylchlorosilane (BDMCS), and octyldimethylchlorosilane (ODMCS) reacted with silanol groups on the surfaces of the pores producing covalent Si-O-Si bonds. Self-condensation between alkylsilanols produced a residue on the surface, which was partially removed using a pure scCO(2) rinse. The hydrophobicity of the blanket p-MSQ surface was recovered after silylation treatment as shown by contact angles >85degrees. The initial dielectric constant of 2.4 +/- 0.1 increased to 3.5 +/- 0.1 after oxygen plasma ashing and was reduced to 2.6 +/- 0.1 by TMCS, 2.8 +/- 0.1 by BDMCS, and 3.2 by ODMCS.