Bias-dependent etching of silicon in aqueous ammonia

Electrochemical characteristics of the bias-dependent etching of silicon in an aqueous ammonia system were experimentally studied with the three-electrode method. The open-circuit potential (OCP) and the passivation potential (PP) for the etching shifted with changes of flow rates, temperature, and concentration of etchants. Considering these correlations, the operation conditions for the nonbiased selective etching of one type over the opposite type (the nonbiased dopant selective etching) were obtained. The OCP was not affected by the etchant flow rate, but the PP shifted in the anodic direction when the flow rate increased for both dopant types. When the PP of the N-type became lower than the PP of the P-type, the etching of the N-type was stopped and the P-type was dissolved naturally. The PP of the P-type had an abrupt cathodic shift with decrease of the solution temperature, though the PP of the N-type was not affected by the temperature. However, the OCP of the P-type gradually shifted in the anodic direction with decreasing temperature.<>