Silicon Oxidation Studies: Morphological Aspects of the Oxidation of Polycrystalline Silicon

Abstract

Previous studies have shown that the oxide grown from polycrystalline silicon displays degraded reliability in terms of higher leakage current and premature dielectric breakdown as compared with the oxide grown from single crystal silicon. Present transmission electron microscope studies of the morphology of polycrystalline silicon films and the oxide grown therefrom show several novel features. The polycrystalline silicon becomes rougher after oxidation, the oxide displays thickness undulations which replicate the previous grain boundaries with thinner oxide over grain boundaries, and the oxide forms intergranularly as well as on the free silicon surface. Despite the intergranular oxide formation, the film skin of oxidized polycrystalline silicon does not become significantly more compressive. The surface roughness features of the polycrystalline silicon and oxide and the film stress values are explained by a Si creep mechanism. From these studies some aspects of the reliability of polycrystalline silicon and oxide are understood. © 1980, The Electrochemical Society, Inc. All rights reserved.