Capacitance‐Voltage Measurement Technique as a Tool for In Situ Characterization of Electrochemical Etching of Silicon

Abstract

A new technique of in situ capacitance‐voltage (C‐V) measurements is proposed to characterize the anisotropic etching of silicon in a two‐electrode electrochemical cell. A series of C‐V measurements have been performed on n‐ and p‐type silicon as the voltage is swept from etching to the passivation regime in the electrochemical cell. It is demonstrated that metal‐oxide‐semiconductor C‐V analysis can be applied to identify the silicon etching and the passivation regions. The passivation oxide thickness has been extracted from the C‐V curves over the range of the voltage used in the experiments. The values of the oxide thickness obtained from the C‐V measurements are compared with those obtained from ellipsometric and spectroscopic measurements, and the discrepancies are explained on the basis of a varying dielectric constant value of the passivation oxide. For a passivation oxide film thickness greater than 300 Å, the dielectric constant approaches 6, whereas for thinner films, a much higher value is obtained. It has been shown that the growth rate of passivation oxide is much higher for p‐silicon compared to n‐silicon. The passivation potential has also been inferred from the C‐V curves. © 1999 The Electrochemical Society. All rights reserved.