Formation mechanism and structures of buried oxy-nitride layers produced by ion beam synthesis

Abstract To synthesize buried compound layers, reactive ions N + , O + and NO + of energy 200 keV atom −1 were implanted into (100) single crystal silicon. Implanted specimens were annealed at 1200°C for 2 h, and analysed by Rutherford backscattering and ion channelling to assess the radiation damage and impurity distributions. SIMS was used to provide further information on the impurity depth distribution and cross-sectional TEM was used to assess the quality of the silicon overlayer and the chemical composition of the buried layer. It was found that when nitrogen is implanted into a wafer which has previously received a high dose of oxygen, the nitrogen moves to the wings of the distribution to form an oxy-nitride. The presence of nitrogen during the subsequent anneal is found to lead to an improvement in the quality of the silicon overlay. A similar improvement is observed for NO + implants into silicon where a single layer of oxy-nitride is formed. However, if a small dose of oxygen is implanted after the nitrogen, a structure containing twinned defective silicon results. From these results the mechanisms responsible for these structures can be reassessed and are discussed in terms of the solid solubility and self diffusion of the impurity within the matrix.