Measurements of Minute Lattice Distortions in Silicon Crystals by X-Ray Double-Crystal Topography Using Extremely Asymmetric Reflection

Abstract

Reflection X-ray topography using double-crystal arrangement has been applied to the observation and the evaluation of lattice distortions in the near-(100)-oriented surface of silicon crystals. A series of X-ray topographs were taken with extremely asymmetric 311 reflection of CuKα1 radiation at a glancing angle of approximately 0.20° near the critical angle of total reflection. The experimental condition is realized using wafers with the (100) lattice plane inclined to the surface at an angle Δα (approximately 2.6°), which usually are used as substrates for epitaxially grown films. Both the local lattice misorientation induced at the boundary of oxide-deposited films of 4–5 nm thickness on a silicon wafer and the surface distortions arising through the processes of mechanochemical polishing and epitaxial growth are clearly visualized as a result of low background noise from the bulk layer due to a shallow X-ray penetration depth of several tens nanometers. From a series of topographs taken by changing the glancing angle from a low angle to a high angle of the Bragg peak at intervals of 5 arcsec, the average tilt angle of lattice planes localized at the oxide film edges was estimated.