Templated nanoporous spin-on glass for high density interconnect applications

This work focused on the development, characterization, and optimization of the properties of silsesquioxane-based, low dielectric constant porous materials for use in high density interconnect applications. The goal was to modify a commercially available spin-on-glass (methylsilsesquioxane), and introduce porosity into the films to lower the effective dielectric constant of the silsesquioxane resin. The pores were created by adding a sacrificial polymer (substituted norbornene polymer) to the silsesquioxane matrix, and then thermally decomposing the sacrificial polymer within the films to form nano-size voids (~5 nm). Studies of the pore size and distribution, pore interconnectivity, chemical bonding of the sacrificial polymer to the spin-on-glass, and the mechanical, electrical and optical properties of the films have been performed. Transmission electron microscopy experiments were conducted to investigate the pore size distribution as a function of molecular weight, concentration and type of functional groups within the sacrificial polymer, and polymer loading level. The mechanical properties were investigated using nanoindentation techniques, and, in general, it was shown that the porous films had superior fracture toughness (resistance to cracking) compared to those without pores