PROBE BEAM DEFLECTION STUDY OF P-SI ELECTRODISSOLUTION IN ACIDIC FLUORIDE MEDIUM IN THE OSCILLATING REGIMES

The 'mirage' or probe beam deflection (PBD) technique has been used to investigate Si dissolution in acidic fluoride in the regime of electr opolishing, in which the electrode surface is covered by a thin oxide film. During current oscillations at a constant applied potential, the variations of the dissolution rate basically reflect variations in th e rate of oxide film formation. During potential oscillations at a con stant imposed current, the dissolution rate varies with the same perio dicity as the potential, with a maximum when the potential is low and a minimum when it is high. Results indicate a correlation between phys ico-chemical and electronic properties of the oxide film, which appear s more prone to etching in its less passivating form and vice versa. ( C) 1998 Elsevier Science S.A. All rights reserved.