STUDY OF SILICON-ON-INSULATOR STRUCTURES FORMED BY LOW-DOSE OXYGEN AND NITROGEN IMPLANTATION

The aim of this work was to study the formation of silicon-on-insulator (SOI) structures produced by the double implantation of low dose (10(16)-10(17) cm-2) oxygen and nitrogen ions into silicon. Secondary ion mass spectrometry (SIMS) analyses were carried out on the materials, both in the as-implanted state and after annealing at a range of temperatures and times. Selected samples were also studied using cross-sectional transmission electron microscopy (XTEM) and Rutherford backscattering (RBS). In the as-implanted state, varying the sequence and the dose of the double implants produced very different and interesting behaviour. When oxygen was implanted before nitrogen, both the oxygen and nitrogen profiles were seen to shift deeper into the SOI structure than expected. However, when nitrogen was implanted first, a shift was not observed. On annealing these materials, the optimum annealing conditions were found to be 1200-degrees-C for 2 h. This produced very good quality materials with buried layers that had sharply defined interfaces. XTEM studies showed the buried layer to be continuous with the thickness and depth of the layer agreeing with the corresponding SIMS profile.