SiO2-like films are deposited in a low-pressure rf helicon reactor using oxygen-rich O-2/TEOS (tetraethoxysilane) mixtures. A model based on the deposition rate variation with the distance to the TEOS injection is used to estimate the TEOS electron-impact dissociation coefficient k(e) and the effective sticking coefficient of reactive fragments s. In the helicon diffusion chamber where the electron temperature and density are about 4 eV and 10(10) cm(-3), respectively, k(e) and s are found to be 1.82 X 10(-7) cm(3) s(-1) and 0.035, respectively. Under these low-pressure plasma conditions, the TEOS dissociation by electron impact is dominant over dissociation by oxygen atoms.