Characterisation of 13C implantations in silicon by NRA [13C(p,?)14N] and RBS

Abstract

SiCX layers close to the surface have been produced by implanting 40 keV 13C ions into silicon with a fluence of 6×1017 at./cm2 (j=12 μA/cm2) at room temperature (RT). Depth distributions and areal densities (doses) of the implanted carbon have been analysed by the nuclear reaction 13C(p,γ)14N (NRA) which shows a sharp resonance in the excitation function at a proton energy of 1748 keV (Γ=75 eV FWHM). The depth resolution at the surface amounts to 31 nm due to energy spread of the proton beam (1.2 keV FWHM) and resonance width. The surface resolution of the NRA can be increased up to 8 nm when tilting the sample (surface normal) to an angle of 75° with respect to the proton beam direction. Using a NaI detector the detection limit of 13C in silicon is approximately 1 at.%. Comparative elastic backscattering measurements with 4He+ projectiles were performed at 2 MeV (Rutherford backscattering spectroscopy, RBS) and 3.45 MeV (high energy backscattering, HEBS) at a backscattering angle of 171°. The measured 13C depth distributions have been compared with a distribution calculated by the Monte Carlo algorithm T-DYN.