Polyhedral oligomeric silsequioxane (POSS) monomer was fixed to a silicon surface by reacting octakis(glycidyldimethylsiloxy)octasilsesquioxane (OG-POSS) with the OH-terminated silicon surface in the presence of tin (II) chloride. The POSS cage layer then served as a nanoporous interlayer to reduce the dielectric constants of polyimide films on silicon surfaces. The chemical structure and surface morphology of OG-POSS modified silicon surfaces were characterized with XPS. With the introduction of a POSS nanopored interlayer, the dielectric constants of polyimide films were reduced.

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Polyhedral oligomeric silsesquioxane nanocomposites thin films on silicon surfaces were prepared by covalent layer-by-layer (LbL) assembly using octakis(glycidyldimethylsiloxy)octasilsesquioxane (OG-POSS) and 4,4(hexafluoroisopropylidene)dianiline (HID) as building blocks. The layer thickness increased linearly with the layer numbers. An ultra-low dielectric constant of approximately 1.57 was found with the LbL thin film. A novel approach to fabricate ultra low-k materials is demonstrated.