Study of Dose and Dose Rate in the Implantation of Nitrogen Isotopes Into Si(100)

Abstract

ABSTRACTIn this paper we address the issue of the dependence of Si3N4 formation on dose dose rate, and target temperature for high dose (up to 3 X 1018 N/cm2) implantation of nitrogen isotopel into Si targets. RBS results for high current (I≈ 30μ/cm2) and room temperature nitrogen implantations indicate that the nitrogen profile and the reduction of the backscattering signal from Si generally appear to be Gaussian. The nitrogen concentration exceeds Si3N4 stoichiometry at the higher doses. Read Camera results indicate the formation of polycrystalline α-Si3N4 and polycrystalline silicon for samples implanted at room temperature and annealed at 1200°C for 2 hours in a 10 Torr vacuum system. For samples implanted at 350 °C and annealed, there is evidence of crystalline α-Si3N4 with fiber texture structure.For low current (〈1 °A/cm2) and room temperature implantation, RBS indicates the formation of a layer whose N/Si ratio is the same as that of Si3N4. Furthermore, the nitrogen profile and the reduction of the Si backscattering signal appear flat. These results suggest that a uniform layer of Si3N4 can be produced providing the supply of nitrogen does not exceed the diffusion rate of nitrogen in compounds formed during implantation.