Silylation of porous methylsilsesquioxane films in supercritical carbon dioxide

Silylation reactions using a supercritical carbon CO"2 solvent were performed on porous methylsilsesquioxane (p-MSQ) thin films. The addition of alkylsilyl moieties to the films repaired damage due to oxygen plasma processing. The films (JSR LKD 5109) were characterized using Fourier transform infrared (FTIR) spectroscopy, ellipsometry, contact angle, and electrical measurements. The silylation chemistries included 80^o. The dielectric constant of ashed p-MSQ was reduced to 2.5, 3.3, and 2.6+/-0.1 by HMDS, TMDS, and TMCS addition, respectively. The mechanism proposed involves the direct reaction of the Si-bearing precursor molecules with the p-MSQ surface. Supercritical CO"2 is a good solvent for silylation reactions and is an effective approach to restore the degradation of porous MSQ films due to plasma ashing.

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