Micro RBS-channeling measurements to study damage accumulation in silicon by ion implantation

Ion implantation is the key technology for electrical doping of silicon. There are many studies of the amorphization of silicon by ion implantation. To extend the investigation of the damage accumulation in silicon to very high ion fluxes, Si samples were implanted with 600 keV Si⁺ ions of a current density of 360 µA/cm² (2.2 x 10¹⁵ Si /(s x cm²)) at different substrate temperatures up to a fluence of 1 x 10¹⁸ Si/cm² by the Bochum super conducting ion projector [1]. The damage of the Si crystal in the implanted circular areas of 185 µm diameter was investigated by micro RBS-channeling with 3 MeV He ions using the Rossendorf nuclear microprobe. For micro channeling measurements a second chamber with a precisely justified 4-axis goniometer was installed behind the chamber used normally for micro ion beam analysis. It allows to investigate the crystal structure in regions down to a size of about 10 µm, keeping the crystal damage during the analysis in check. For this high Si ion flux a significant dependence of the damage accumulation and of the Si amorphization on the implantation temperature and fluence was observed. It was shown that the model of the current density dependence on the amorphization temperature used also by R.D. Goldberg et al. [2] can not be extrapolated to very high ion current densities.

[1] J. Meijer, A. Stephan, Microelec. Eng. 41/42 (1998) 257
[2] R.D. Goldberg, R.G. Elliman, J.S. Williams, Nucl. Instr. and Meth. B 80/81 (1993) 596