A MECHANISTIC STUDY OF SILICON ETCHING IN NH3/H2O2 CLEANING SOLUTIONS

The etching of (100)-oriented n-type silicon in NH3/H2O2 solutions at 70°C was studied by kinetic and electrochemical measurements. In solutions with a H2O2 concentration below 3 × 10−3M etching is observed, while dissolution is inhibited when the H2O2 concentration exceeds this critical value. In the latter case the silicon surface attains a potential in a range in which the surface is passivated. As alkaline H2O2 solutions decompose, the H2O2 concentration decreases in the course of time and etching starts when the concentration drops below the critical value. The kinetics of the homogeneous decomposition reaction was also studied. It is shown that n-type silicon can be anodically oxidized in the dark. A mechanism is proposed which accounts for the etching process, the anodic dissolution, and the inhibition at high H2O2 concentrations. © 1990, The Electrochemical Society, Inc. All rights reserved.