A study of residual stress distribution through the thickness of p/sup +/ silicon films (thermal oxidation effects)

The effect of thermal oxidation on the residual stress distribution throughout the thickness of heavily-boron-doped (p/sup +/) silicon films is studied. The deflection of p/sup +/ silicon cantilever beams due to residual stress variation throughout 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 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.>