Anodic Dissolution and Passivation of Silicon in Hydrazine

Abstract

Anodic dissolution and passivation of silicon in aqueous hydrazine has been studied. The current‐voltage characteristics of anodic‐biased silicon wafers, (100) oriented n‐ and p‐type with various doping concentrations, in hydrazine were examined. It is found that there is a critical current density for anodic biased silicon to be passivated in hydrazine solution. A mechanism of p‐n junction etch‐stop is proposed in which p‐n junction leakage current and critical passivation current density (CPI) are two determining parameters. For n‐type silicon, the CPI is found to be about 60 μA/mm2, independent of its resistivity; whereas for p‐type silicon the CPI depends on silicon resistivity. The different behavior of anodic biased n‐ and p‐type silicon wafers in hydrazine is attributed to the existence of surface states and their effects on the surface potential as well as the availability of holes at surface.