Evaluation on Pore Structures of Organosilicate Thin Films by Grazing Incidence Small-Angle X-ray Scattering

Nanoporous thin films fabricated by both a core-shell-shaped organic-inorganic hybrid sphere (octa(2,4-dinitrophenyl)silsesquioxane, ODNPSQ) and a four-leg-numbered surfactant (polyoxyethylene sorbitan monolaurate, Tween-20) for porogens in a higher molecular weight precursor (polyphenylsilsesquioxane, PPSQ) were characterized, respectively, by grazing incidence small-angle X-ray scattering (GISAXS), and the measured 2D GISAXS profiles were analyzed quantitatively by using a GISAXS formula based on the distorted wave Born approximation (DWBA). The fitted 2D GISAXS data show that the PPSQ porous thin films imprinted with ODNPSQ porogen exhibit sphere-shaped closed pores with the average pore size within a range of 1.18-3.12 nm and pore size distribution widths about 3.0 nm when the porogen loadings increase from 10 to 40 wt % and those imprinted with Tween-20 porogen give out an average pore size of 1.07-1.29 nm and pore size distribution widths about 2.0 nm with the porogen loading varying from 5 to 30 wt %. The nanoporous dielectric thin films imprinted with ODNPSQ porogen show a reducing to the molecular aggregation of porogens and significant antiphase separation behavior in the cross-linked matrix.