In Situ Infrared Observation of Etching and Oxidation Processes on Si Surfaces in NH 4 F Solution

Abstract

We use infrared absorption spectroscopy in the multiple internal reflection geometry to investigate in situ and in real‐time the chemical process at Si(100) surfaces that are immersed in a dilute solution of ammonium fluoride, . We have followed spectral changes in the Si‐H stretch vibration region of the surface during immersion in the solution. Infrared spectroscopic data show that the native oxide on the surface is initially removed by solution and subsequently, H‐terminated Si(111) microfacets are increasingly populated. Long‐term immersion in dilute leads to oxide formation on the surface. The rate of oxide formation strongly depends on the concentration of ; oxide formation is enhanced at concentrations below 10% and it does not occur at concentrations above 20%. We suggest that oxide formation and subsequent oxide removal proceed on Si surfaces in dilute solution and that at low concentration, the rate of oxide formation is higher than that of oxide removal. © 2000 The Electrochemical Society. All rights reserved.