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

Abstract

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 (Tp) or annealing time (tp). The film density also increases as Tp or tp increases and we conclude that annealed films have become denser as compared to the as-deposited films. We also suggest that increasing tp would be more efficient than raising Tp for film densification. Infrared spectrum analysis results show that with increasing Tp or tp, 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 Å of the oxide at the Si–SiO2 interface and that the Si–SiO2 interface is not abrupt.