Effect of thermal oxidation on residual stress distribution through the thickness of p/sup +/ silicon films

Abstract

The authors investigate the effect of thermal oxidation on the residual stress distribution through the thickness of p/sup +/ silicon films. The deflection of p/sup +/ silicon cantilever beams due to residual stress variation through the film thickness is studied for as-diffused and thermally-oxidized films. Cantilevers of as-diffused p/sup +/ silicon films display a positive curvature (or a negative bending moment), signified by bending up of the beams. Thermal oxidation of the films prior to cantilever fabrication by anisotropic etching modifies the residual stresses in the p/sup +/ film, specially in the near-surface region (i.e. the top 0.3 mu m to 0.5 mu m for the oxidation times used here), and can result in beams with a negative curvature even when the oxide is removed from the p/sup +/ silicon cantilever surface subsequent to cantilever fabrication. Excluding the near-surface region, for the diffusion and oxidation times studied, the residual stress distribution through the remainder of the p/sup +/ silicon film thickness is such that a positive curvature of the cantilevers results even when oxidation is performed. >