In-situ detection of stress in oxide films during Si electrodissolution in acidic fluoride electrolytes

We report on the in-situ determination of stress in anodic oxide films produced during electrodissolution of silicon crystalline electrodes in acidic fluoride media. The characterization is accomplished with the bending beam method (BBM) using thin (35 mm) Si cantilever electrodes. The oxide stress has been calculated with an improved version of Stoney’s equation which takes into account the difference of Young’s modulus between silicon substrate and oxide layer. The stress is about 220 MPa for very thin oxide films (tB10 nm). Various possible contributions to electrode bending — oxide stress, surface tension effects and film electrostriction — are considered and their relative incidence is then discussed. Analysis of the curvature signal detected during the occurrence of the electrochemical oscillations results in a better understanding of the phenomena.