Etch rates of anodic silicon oxides in dilute fluoride solutions

The etch rates of anodic oxides in dilute fluoride solutions have been determined by using a new approach to the analysis of anodic current oscillations. The variation of the thickness of the anodic oxide with time has been measured by in situ Fourier transform infrared spectroscopy. The change in oxide thickness can be simulated by considering the time-dependent current and the etch rate of the oxide in the HF-containing solution. The pH-dependent etch rates can be well fitted for different concentrations of NH₄F by applying Judge's model [J. Electrochem. Soc., 118, 1772 (1971)]. The coefficients in Judge's model are obtained for the etching process of the respective anodic oxides. The electronic properties of the Si/anodic oxide interface, which have been investigated by in situ photovoltage and photoluminescence measurements, correlated with the anodic current.