DEFECTS IN OXYGEN-IMPLANTED SILICON

Silicon-based devices in their various representations use ion implantation for the electronic modification of the basic material. The defects and their formation by ion beam must be identified and minimized to obtain a useful product. We report the characterization of defects formed during oxygen implantation of silicon using conventional and high-resolution transmission electron microscopy. The effect of wafer temperature as the parameter most influential on type and density of defects was investigated. The study revealed that microtwins and stacking faults were created in the top silicon layer during implantation from 450-550-degrees-C. From 600-700-degrees-C, numerous multiply faulted defects were observed. They are 40 to 140 nm long and consist of several discontinuous stacking faults which are randomly spaced and separated by six to twelve atomic layers. In the substrate region beneath the buried oxide layer created by implantation, the defects observed included stacking faults and {113} defects. Some parts of the {113} defects show a twinning structure across {115} planes. Some are converted into a hexagonal structure. After annealing at 1300-degrees-C for 6 hours in argon, samples implanted at 450-575-degrees-C contain dislocation densities higher than those implanted above 575-degrees-C. Details of the structure and formation mechanisms of these defects will be discussed.