Determination of the carbon depth profiles of (Si1CxCy)-C-12-C-13 layers using RBS and NRRA

Si-1 C-12(x) C-13(y) layers were prepared by successive implantation of the carbon isotopes C-12 and C-13 into c-Si(1 1 1). The samples were kept near RT. Ion energy was 40 keV. Ion fluences ranged from 2 x 10(17) to 6 x 10(1 7) ions/cm(2). The total carbon concentration (C-12 and C-13) was Obtained by Rutherford backscattering spectrometry (RBS) using 1.8 MeV He-4(+) proje ctiles and a backscattering angle of 171 degrees. Its depth distribution wa s determined by simulating the backscattering yield of the near surface sil icon part of the spectrum where the yield is reduced due to the presence of the implanted carbon. The C-13 depth distributions were measured using the narrow resonance of the nuclear reaction C-13(p,gamma)N-14 at E-res = 1748 keV. The raw data of this measurement (gamma-yield vs proton beam energy) and the data of the RBS simulation were converted to concentrations depth p rofiles of the C-12 and C-13 isotopes with a common depth scale by means of a new developed computer algorithm. (C) 2000 Elsevier Science B.V. All rig hts reserved.