Positron spectroscopy of vacancy-type defects in Si created by 5 keV implantation

Abstract

Structural damage resulting from the implantation of 5 keV B + ions into FZ-Si has been investigated by positron annihilation spectroscopy (PAS) using a tuneable monoenergetic beam. Four samples, exposed to ion fluences from 2 × 10 12 to 2 × 10 15 cm −2 , were studied. The PAS results demonstrate the applicability of the technique to the study of vacancy-type defects in small-scale device structures created by very low-energy ion implantation. Ion depth profiles determined by SIMS exhibited tails extending well beyond the limit predicted by the code TRIM, attributed to ion channelling. PAS, when extended by repeated measurements after precise etching of 40 and 140 nm of material via anodic oxidation, showed that the vacancy-type defect depth profiles also extended far beyond the limit predicted by TRIM. The ratio of defects to ions increases with depth, suggesting that the defect tails are not simply correlated to the implanted ions but that there may also be a contribution from post-implantation defect diffusion.

Direct high-resolution determination of vacancy-type defect profiles in ion-implanted silicon

“…The principle of enhanced-depth-sensitivity VEPAS has been discussed by Knights, Coleman and co-workers [3][4][5] and by Krause-Rehberg et al [6], and applied by Knights et al [7], Malik et al [8] and Janson et al [9] to study deep defect tails, Simpson et al [10] to study damage caused by ions implanted through a SiO 2 layer, Fujinami et al to study damage in He-implanted Si [11], Saarinen et al and Kauppinen et al to study vacancy distributions in In-implanted GaAs and MeV proton-implanted Si [12,13] and Krause-Rehberg et al [14][15][16] to study damage caused by sawing GaAs wafers and impurity gettering at half-ion range in self-implanted silicon. In [7] and [8] simple one-or two-step etching was performed using anodic oxidation as an intermediate stage (as discussed later). In [9] etching was performed using an inductively coupled plasma system.…”