Measurements of minute lattice distortions in silicon crystals by X-ray double-crystal topography using extremely asymmetric reflection

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 CuKalpha1 radiation at a glancing angle of approximately 0.20degrees 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 Deltaalpha (approximately 2.6degrees), 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.