X-Ray Topographic Observations of Minute Lattice Distortion near the Surface of (100) Silicon Crystals

Abstract

The characterization of minute lattice distortion in mirror-polished (100) silicon wafers was performed by the Berg-Barrett method using the extremely asymmetric X-ray diffraction of the 311 reflection with CuKα1 or CuKβ radiations. A series of X-ray topographs were taken at a glancing angle of 0.15–0.20° near the critical angle of total reflection. This experimental condition is realized using the diffraction geometry of the specimen surface making angles Δα (approximately 2.60° and -0.28° for CuKα1 and Kβ, respectively) with the (100) lattice plane. For silicon wafers with 25-nm-thick oxide films, the local variation in the orientation of the lattice plane occurring at the film boundary was observed, and lattice distortion images near the surface produced by the mechanochemical polishing were clearly visualized.