A Mechanistic Study of Silicon Etching in NH 3 / H 2 O 2 Cleaning Solutions

The etching of (100)‐oriented n‐type silicon in solutions at 70°C was studied by kinetic and electrochemical measurements. In solutions with a concentration below etching is observed, while dissolution is inhibited when the 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 solutions decompose, the 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 concentrations.