CONTRAST OF DEVICE STRUCTURES IN X-RAY SECTION TOPOGRAPHS

The images in x-ray section topographs arising from the strain associated with devices fabricated on silicon wafers have been simulated using Takagi's theory and the isotropic elasticity model of Blech and Meieran. Simulated images of the edges of oxide films and diffused regions are found to be in very good agreement with experiment without recourse to the correction factors necessary in earlier work. The value of the force per unit length at the device edge, deduced from fitting simulation to experiment, was in agreement with that deduced by earlier workers using ray optical theory. Variation in image structure with force per unit length at the device edge and device position in the Borrmann fan has been studied and it has been shown that, due to the cancelling of strains from opposite edges of the device, the minimum device width detectable on a section topograph is approximately 1 mum.