Stabilizing dielectric constant of fluorine-doped SiO2 film by N2O and NH3 plasma post-treatment

Fluorine doped oxide (SiO2-xFx) films have been found to exhibit a low dielectric constant. However, the critical issue about SiO2-xFx is its low resistance to moisture which causes the dielectric constant of the film to increase with time. In this work, N2O and NH3 plasma post treatments are applied to as-deposited SiO2-xFx films. It has been observed that NH3 plasma post-treatments of SiO2-xFx are quite efficient at blocking moisture. The dielectric constant and stress values of the SiO2-xFx films after the N2O and NH3 plasma post-treatments are very stable. The disadvantage of N2O plasma post-treatment is that the dielectric constant of the SiO2-xFx film increases from 3.21 to 3.6 due to fluorine desorption from the SiO2-xFx network. On the other hand, NH3 plasma post-treatment is more efficient at blocking moisture and keeping the low dielectric constant unchanged due to surface nitridation of the SiO2-xFx film. (C) 1997 Elsevier Science S.A.