GROWTH-KINETICS AND STEP COVERAGE IN PLASMA DEPOSITION OF SILICON DIOXIDE FROM ORGANOSILICON COMPOUNDS

The aim of this work is to compare the step coverage of aluminium strips by SiO2 obtained with different silicon sources: SiH4, hexamethyldisiloxane (HMDSO), tetraethoxysilane (TEOS); and to correlate the evolution of the step coverage with the deposition kinetics. The profiles of the films deposited using SiH4 obtained by scanning electron micrographs of cross-sections show an isotropic deposition and a low surface mobility. The shape of the profile is independent of substrate temperature as well as of the deposition rate. Profiles obtained when using HMDSO depend on substrate temperature: at high temperature the profile exhibits a good step coverage, while at low temperature the profile shows less conformality and is representative of a directional growth. Nearly identical results are observed with TEOS at deposition temperatures above 200-degrees-C. It is found that with organosilicon compounds the deposition rate decreases with an increase of the deposition temperature T(S) from 25 up to 400-degrees-C for HMDSO and from 200 up to 400-degrees-C for TEOS. It is also found that adsorption-desorption phenomena are among the most important factors for step coverage and that at low deposition temperatures the film growth rate is quite sensitive to ion surface bombardment and results in a non-conformal deposit even in compounds with high surface mobility.