Photoacoustic Characterization of Ion-Implantation Damage in Silicon

Abstract

The properties of silicon substrates damaged by self ion-implantation into silicon has been studied by PZT photoacoustic (PA) spectroscopy. The PA spectra in the samples after implantation had a peak near the band-edge and a long decreasing tail towards the shorter wavelength side predominantly due to the wavelength dependence of light transmission depth. As the PA signal at this shorter wavelength range was found to be sensitive to the extent and the structure of damage present in the implanted layers, the PA signal intensity within this range was used for characterizing the implantation-damage. The result indicates that the damage significantly affects the PA signal intensities and it is annealed out through at least four well-defined stages:a largely increasing stage and a largely decreasing stage at 300–450 ℃ and at 450–700 ℃, respectively, and moreover, a slightly increasing stage and a slightly decreasing stage at 750–850 ℃ and at 850–950 ℃, respectively. The first stage suggests the reordering from a highly disordered layer to a crystalline one including a large number of complex defects, the second stage the extinction process of these defects, and the third and fourth stages the generation and extinction of dislocation loops.