Si-N Bonding at the SiO2/Si Interfaces During Deposition of SiO2 by the Remote Pecvd Process

Abstract

Thin films of SiO2 were deposited on Si substrates by remote PECVD following an in-situ cleaning/surface passivation with atomic-H. Si-N bonds were found in the immediate vicinity of the SiO2/Si interface when nitrous oxide, N2O, was used as O-atom source gas in the remote PECVD process. Si-N bonds, as well as Si-surface roughening produced by H-atom etching, contribute to the formation of high densities of midgap trapping states, Dit ∼1011 cm−2eV−1, at the SiO2/Si interface. Eliminating the H-atom processing step, and exposing the Si surface to plasma-generated O-atoms prior to the SiO2 deposition: i) eliminated Si-N bonding at the Si/SiO2 interface; ii) reduced midgap Dit to ∼1−3×1010 cm−2eV−1; iii) eliminated surface roughening; and iv) improved process latitude and reproducibility.