Measurements of Lattice Distortions near Silicon Surfaces Implanted with Low-Energy Nitrogen Ions by Reflection X-ray Topography

Mirror-polished Czochralski-grown wafers with near-(100)-oriented surfaces were implanted with N^+ at 8 keV energy at a dose of 1 × 10^<15>cm^<-2>. Lattice distortions produced by the implantation process were observed by X-ray double-crystal topography using extremely asymmetric 311 reflection of Cu K α_l radiation at a glancing angle of approximately 0.25° near the critical angle of total reflection. The intensity contrast caused by the lattice extensions in thin layers was clearly visualized. By annealing at 700°C for more than 90 min, the imperfect crystal in the ion-implanted region evidently recovers to a more perfect one, except for the boundary of the implanted region. The lattice distortions at the boundary, consisting of a narrow striated region, are thought to be due primarily to variations in the lattice spacing that has been deformed nonelastically. From a series of topographs taken by changing the glancing angle from a low-angle to a high-angle of the Bragg peak in steps of 5 or 10 arcsec, the differences in lattice spacing between the striated portions and the unimplanted regions were estimated