Reduced defect density in silicon-on-insulator structures formed by oxygen implantation in two steps

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Abstract
Up to now, the best quality silicon-on-insulator material formed by high-dose oxygen ion implantation has been produced by conventional one step implantation and subsequent high-temperature annealing. Nevertheless, it still contains structural defects: threading dislocations in the top silicon film and silicon islands inside the buried SiO2 layer. This letter presents a new method for producing silicon-on-insulator structures using sequences of oxygen ion implantation and high-temperature annealing steps. The structures obtained using this method are nearly free from defects observable by electron microscopy. In particular, no threading dislocations could be observed and the density of silicon islands is reduced by several orders of magnitude. A mechanism of Si interstitial atoms migration is proposed to explain these observations in accordance with other studies.