X-Ray Extinction Contrast Topography of Silicon Strained by Thin Surface Films

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Abstract
Diffraction topographs of oxidized silicon wafers made by the extinction contrast technique show extremely high intensity being diffracted from the silicon surface directly under steps etched in the oxide. Edges of metal or dielectric films evaporated on silicon similarly show enhanced intensity. In some cases, a decreased diffracted intensity (less than that diffracted by pure Si) is seen in these regions. These two effects are attributed to elastic strain transmitted to the Si by the step or edge, due to the adherence of the film to the substrate. Enhanced intensity is due to extinction contrast, while decreased intensity is due to a Borrmann anomalous transmission effect. The orientation of the step with respect to the diffraction vector ghkl, the height of the step, and the compositions of substrate and film are shown to be important parameters affecting the diffracted intensity.