Low-k Interlayer Dielectric Materials: Synthesis and Properties of Alkoxy-Functional Silsesquioxanes

Abstract

Two new types of silsesquioxanes, (HSiO3/2)x[(tBuO)SiO3/2]z or THQ and (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z or THTRQ (R = octadecyl), were synthesized and studied as low-k dielectric materials for electronic applications. The materials were prepared by cohydrolysis and condensation of alkoxy monomers, (AcO)2Si(OtBu)2, HSi(OEt)3, and CH3(CH2)17Si(OMe)3. Spectroscopic data supported retention of tertiary alkoxy groups [(tBuO)SiO3/2 or (tBuO)2SiO2/2] and presence of silanol. The molecular weight of (HSiO3/2)x[(tBuO)SiO3/2]z increased with the T/Q ratio, while that for (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z exhibited less dependence on composition. The tert butoxy groups were eliminated in both materials at low temperatures (<450 °C), and subsequent decomposition of octadecyl group (R) in (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z occurred through cleavage and re-distribution of carbon−carbon bonds (430−550 °C). Heating at 450 °C for 2 h afforded porous solids. The total pore volume of materials derived from (HSiO3/2)x[...