Damage profiles determination in ultra-shallow B + implanted Si by triple crystal X-ray diffraction and transmission electron microscopy

Abstract

B + ions were implanted in Si at ultra-low energies: 0.25, 0.5 and 1 keV, respectively, and at different doses: 1×10 14, 1×10 15 cm −2. Lattice distortion and disorder due to the implantation process were investigated by means of a high resolution X-ray diffraction method. Due to the very low implantation depth (a few nm), the X-ray diffraction measurements were carried out by triple-crystal diffractometry. With this experimental configuration it was possible to separate coherent from diffuse scattering, considerably improving the signal-to-noise ratio. For the analysis of the experimental curves, the subsurface region was divided in several thin layers. The layer thickness, the static Debye–Waller factor, which is related to the lattice damage, and the lattice spacing modification (strain) were the parameters of the fitting procedure. Despite the small thickness of the ‘subsurface-damaged area’, it was possible to obtain the main parameters describing the depth distribution of the lattice distortions in the analyzed crystals. Transmission electron microscopy investigations were made on two samples implanted at the lowest energies and the results obtained by the X-ray diffraction were confirmed.