Near-Surface Damage and Contamination after CF₄/H₂ Reactive Ion Etching of Si

Abstract

Silicon surfaces which had been exposed to CF4/40%H2 reactive ion etching have been characterized by x-ray photoelectron emission spectroscopy, He ion channeling, H profiling, and Raman scattering techniques. Plasma exposure of a clean Si surface leads to the deposition of a thin (∼30-50Å thick) C, F containing film. The near-surface region (-30-50A) of the Si substrate is heavily disordered (“amorphized”), as found by ion channeling and Raman scattering. A modified, less damaged Si region extends from about 30-50Å from the surface to a depth in excess of 250Å. This layer contains a high concentration (∼5 atom percent) 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 the H is bonded to the Si lattice. In ion scattering, the extended modified Si layer appears to cause a strongly enhanced background in the energy spectra. Results of Monte Carlo range calculations are reported and compared with the damage depth found experimentally. © 1985, The Electrochemical Society, Inc. All rights reserved.