Moisture uptake and dielectric property of methylsilsesquioxane/high-temperature porogen hybrids and porous low-k films

Abstract

Two high-temperature pore generators (porogens) have been used to study the effect of porogen structure on moisture uptake and k-value in methylsilsesquioxane/porogen hybrid films and their corresponding porous films in a postintegration porogen removal scheme. Poly(styrene-b-4-vinylpyridine) containing di-block structure and pyridine polar group leads to higher moisture uptake and k-value in the hybrid films as compared to poly(styrene-block-butadiene-block-styrene) with symmetrical structure and nonpolar groups. Moreover, the moisture uptake behavior in both as-prepared hybrid films is in physical sorption mode based on their reversible adsorption-desorption curve measured by quartz crystal microbalance. After porogen removal, the k-values of porous films are favorably not influenced by porogen structures, and their moisture uptake is as low as 1.78 wt% even at 40 vol.% porosity. However, based on the simulation of the modified-Rayleigh model, the porous films are found to possess 0.4 vol.% chemisorbed moisture on the pore surface, resulting in 17-23% deviation from the ideal k-values.