Effect of Curing on the Porogen Size in the Low-k MSQ/SBS Hybrid Films

Abstract

The interaction between a polystyrene-b-polybutadiene-b-polystyrene (SBS) porogen and a low-k methylsilsesquioxane (MSQ) matrix under different curing profiles and their impact on porogen size were studied by grazing incidence small-angle X-ray scattering, viscosity measurement, and Fourier transform infrared analysis. For slow curing, significant porogen diffusion and aggregation occurred between 100 and 170 degrees C, at which the porogen size increased from 12 to 32 nm. The interaction mechanism between porogen and the MSQ matrix and its correlation with porogen size during the thermal cure process were elucidated. The aggregation of the SBS porogen was greatly influenced by the microstructure of the MSQ matrix at three controlling temperatures; namely, (1) glass transition temperature, T(g) (similar to 100 degrees C), (2) onset temperature (160 degrees C) for transforming cage to network structure, and (3) immobilization temperature (170 degrees C). In contrast, a rapid curing rate enabled the formation of small porogen size (similar to 12 nm) in the hybrid films and yielded better mechanical strength. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3529246] All rights reserved.