Effect of rf power on remote-plasma deposited SiO2 films

Abstract

Significant improvement in material and electrical properties of SiO2 films deposited by low-temperature remote plasma-enhanced chemical vapor deposition take place as the rf power to the plasma discharge is increased. The deposition rate increases, and the index of refraction at 632.8 nm, the frequency of the dominant Si—O—Si bond-stretching vibration in the infrared absorption spectrum, the etch rate, and the static dielectric constant of the remote-plasma deposited films all approach those of thermally grown SiO2 films with increasing rf power to the plasma discharge. The total compressive stress in the oxides deposited at high power, ∼300 W, is about 20% higher than that in oxides deposited at lower power, ∼30 W. Comparison of film properties with those of plasma-deposited substoichiometric oxides (SiOx, x≤2) and thermally grown stoichiometric oxides SiO2 leads us to conclude that (i) the films deposited at rf levels from 10 to 300 W are homogeneous stoichiometric oxides SiO2, (ii) correlated variations in the film properties at the higher powers are consistent with a densification of the film, and (iii) systematic changes in the material properties take place along a linear path between two previously identified network morphologies on an n vs ν phase diagram.