Densification of radio frequency sputtered silicon oxide films by rapid thermal annealing

A study of the densification of radio frequency sputtered silicon oxide films by rapid thermal annealing was undertaken using both physical (etching, refractive index, and density calculation) and structural [infrared and x-ray photoelectron spectroscopy (XPS)] techniques. It was discovered that the etch rate of annealed films is reduced drastically, compared with as-deposited films and that the refractive index increases with increasing annealing temperature (T-p) or annealing time (t(p)). The film density also increases as T-p or t(p) increases and we conclude that annealed films have become denser as compared to the as-deposited films. We also suggest that increasing t(p) would be more efficient than raising T-p for film densification. Infrared spectrum analysis results show that with increasing T-p or t(p), Strain in the films has become more relaxed, and a significant amount of the surface hydroxyl groups in the annealed films was removed. The XPS analysis results show that a substantial amount of suboxide species exist within 30-40 Angstrom of the oxide at the Si-SiO2 interface and that the Si-SiO2 interface is not abrupt. (C) 1998 American Institute of Physics.