High quality silicon on insulator structures formed by the thermal redistribution of implanted nitrogen

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Abstract
Silicon wafers have been implanted with 200-keV 14N+ ions to doses between 0.25 and 1.4×1018 N+ cm−2 at a temperature of 500 °C and have been annealed at 1200 °C for 2 and 8 h. Rapid redistribution of the implanted nitrogen occurs, against the macroscopic concentration gradient, in samples implanted with doses below that required to directly synthesize stoichiometric Si3N4. This leads to the formation of a continuous buried layer of either amorphous or polycrystalline Si3N4. The surface layer is high quality single crystal silicon (χmin =0.043) containing no polycrystalline material nor precipitates. The Si-Si3N4 interfaces are extremely abrupt but with an irregularity of ∼100 and ∼50 Å at the upper and lower interfaces, respectively.