High-Amplitude versus Low-Amplitude Current Oscillations during the Anodic Oxidation of p-Type Silicon in Fluoride Containing Electrolytes

Sustained electrochemical oscillations at p-type Si(100) in a dilute ammonium fluoride electrolyte are investigated by means of ellipsometric intensity and hydrogen measurements. Two main types of oscillations are identified, one with a low and one with a high current amplitude. It is demonstrated that the low-current amplitude oscillations do not involve any variations in oxide quality or etch rate. Furthermore, experimental results suggest that the high-amplitude current oscillations emerge from the low-amplitude current oscillations and thus share the feedback loops causing the oscillatory instability. Hence, the origin of oscillations during anodic dissolution of silicon has to be reconsidered.