Structure of pyrolytic and sputtered SiO2 films by X-ray Fourier analysis

Abstract

Structures of pyrolytic and sputtered SiO2 films have been obtained by X‐ray Fourier analysis method. The electron radial distribution function was calculated from experimental X‐ray spectra. Both pyrolytic and sputtered SiO2 films have slightly oxygen deficient SiO4 tetrahedral structures. Sputtered SiO2 has a structure more similar to that of fused silica than pyrolytic oxide. The pyrolytic SiO2 consists of SiO4 tetrahedral units randomly stacked and packed. The SiOSi angles are distributed in such a way in the pyrolytic oxide that no ordering exists beyond a given tetrahedral unit, i.e. ≈︁ 3 Å. Therefore, pyrolytic oxide has a less compact structure or lower specific density, a larger amount of vacancies and pinholes, and, consequently, higher susceptibility to water absorption and higher etching rate than fused silica or sputtered SiO2.