Structural and electrical investigation of high temperature annealed As-implanted Si crystals

Abstract

Si wafers implanted at 80keV with different As doses, and next annealed at different temperatures for different times, were studied by means of x-ray triple crystal diffraction, x-ray standing wave, transmission electron microscopy, spreading resistance profile, and electrochemical C-V profiling methods. The implantation processes produced heavily damaged subsurface regions hundreds of nanometers deep. By fitting both the x-ray diffraction curves and the x-ray standing wave photoelectron emission profiles, it was possible to determine the most appropriate strain and atomic static displacement behavior versus depth within the disturbed region of the crystal. The results obtained by x-ray diffraction measurements were confirmed by transmission electron microscopy investigations. Therefore, making use of different structural and electrical characterization techniques it was possible to find: (i) the depth of amorphization of the implanted regions, (ii) the appearance of extended defects (dislocation loops band) during the restoration of the lattice by the annealing processes and the dependence of their size and density on the implant dose and the annealing time and temperature, (iii) the dopant profiles versus depth as a function of the implant dose and the annealing parameters, (iv) the effect on the total strain of the doping induced variation of the conduction band minima. The experimental evidence of a screen electronic effect on the As+–Si distance in the restored crystal lattice was confirmed by ab initio calculations.