MONOSILANE ADSORPTION AND INITIAL GROWTH-STAGES OF SILICON LAYERS ON THE (100) AND OXIDIZED SILICON SURFACES - ELLIPSOMETRIC INVESTIGATION

Monosilane adsorption kinetics on (100) and oxidized silicon surfaces has been studied by means of a fast-response ellipsometer. Monosilane adsorption on the (100) silicon surface is irreversible and has no activation barrier in the temperature range 20-500-degrees-C. Condensation coefficients of SiH4 for the closed and the flowing adsorption technique are sigma = 7 X 10(-3) and 5 X 10(-2), respectively. The thickness of the adsorption layer increases in the temperature range 125-350-degrees-C which is evidence for the formation of a surface supermonolayer coverage. At T > 350-degrees-C decomposition of adsorption complexes takes place, accompanied by hydrogen desorption. This process is characterized by an activation energy of E = 44 +/- 2 kcal/mol. Monosilane is adsorbed reversibly on the oxidized silicon surface in the temperature range 350-490-degrees-C and at a pressure of P < 5 X 10(-2) Torr. At pressures P > 5 X 10(-2) Torr adsorption complexes decompose and amorphous silicon grows. The growth rate is directly proportional to the monosilane pressure in the gas phase and increases with increasing temperature; the activation energy of this process is E = 56 +/- 6 kcal/mol. The analysis of the kinetic curves indicates that the growth of amorphous silicon is a chain process at the initial stage.