Anisotropic Dry Etching of S1O2 on Si and its Impact on Surface and Near-Surface Properties of the Substrate.

Abstract

AbstractIn the present paper structural and chemical changes which can occur in the surface and near-surface properties of the substrate during anisotropic dry etching of SiO2 on Si will be reviewed.Silicon specimens which had been etched in CF4/X%H2 (X≤40) have been characterized by X-ray photoelectron emission spectroscopy, He ion channeling, H profiling and Raman scattering techniques.Key results of our studies are summarized as follows: Plasma exposure of a Si surface leads to the deposition of a thin (≤50Å thick) C,F-film.A Si-carbide containing Si region is formed during RIE which is localized near the fluorocarbon-film/Si interface.The near-surface region (∼30–50Å) of the Si substrate is also heavily disordered as found by ion channeling and Raman scattering.A modified, less damaged Si region has been found in the case of hydrogen-based etching gases, which extends from about 30–50Å from the surface to a depth in extent of 250Å and contains a high concentration (∼ 5 at.%) of H as shown by hydrogen profiling techniques.From the observation of Si-H and Si-H2 vibrational modes by Raman scattering it has been shown that some of the H is bonded to the Si lattice.