Rutherford backscattering and channelling studies of buried nitride structures directly produced by high intensity ion implantation of nitrogen into silicon

Abstract

Recent work on buried nitride structures has shown that by implanting nitrogen in silicon at sufficiently high beam current densities, or in other words by using the so-called High Intensity Ion Implantation (HIII), it is possible to produce directly stoichiometric layers of Si 3 N 4. Under appropriate conditions of flux, dose and temperature, the HIII of nitrogen appears to have similarities to oxygen implantation in that the composition at the peak of the implant profile saturates at the stoichiometric ratio for Si 3 N 4 while maintaining good crystalline quality in the silicon overlayer. This is a technologically important issue which may warrant a reconsideration of the standard technology with a view to obtaining device-worthy silicon-on-insulator substrates. Buried nitride structures have been directly formed by high energy (1 MeV mol −1) HIII of molecular nitrogen in heat sunk (111) silicon substrates at doses ranging from 7×10 17 to 2.1×10 18 cm −2 and temperatures up to 300°C. Rutherford backscattering and channelling analysis of the as-implanted samples was undertaken to evaluate the distributions of the implanted nitrogen atoms and the extent of radiation damage in the silicon overlayers. It has been found that the resulting structures depend strongly on the dose rate, implant dose, temperature and manner of beam heating. The individual role as well as the combined effect of the above implantation parameters on the degree of near-surface crystallinity, nitrogen distribution, critical dose for direct formation of a Si 3 N 4 layer and upper interface region have been studied and a basis for further optimization has been outlined.