Real-time diagnostics of growth of silicon-germanium alloys on hydrogen-terminated and oxidized silicon (111) surfaces by spectroscopic ellipsometry

Chemical vapor deposition of amorphous hydrogenated silicon-germanium alloy s (a-SiGe:H) was induced by photolysis of disilane and digermane mixtures w ith an ArF laser at 193 nm. The growth behavior on hydrogen-terminated and oxide-covered Si(111) surfaces was studied in real time in the monolayer re gion by spectroscopic ellipsometry (1.2-4.7 eV). One-, two- and three-layer models were employed to simulate the ellipsometric data. For the flat hydr ogen-terminated silicon surface the slow formation of a well-defined monola yer is extracted from the analysis. On the native oxide-covered surface fas t initial 3D growth was observed with coalescence at a larger film thicknes s. A three-layer model was needed to describe the growth of ultrathin films after coalescence, where a third layer, with a thickness in the nanometer range, takes into account the lower quality of the ultrathin film layer nea r the interface. (C) 1999 Elsevier Science S.A. All rights reserved.