Gettering of copper in silicon at half of the projected ion range induced by helium implantation

Abstract

Secondary ion mass spectroscopy, transmission electron microscopy, Rutherford backscattering /channeling spectrometry, and elastic recoil detection analysis measurements were used to determine the Cu gettering behavior induced by He implanted into Si samples. This study was done in an iterative way by changing the implanted He fluence (531015–331016 cm-²), implantation temperature (room temperature or 350 °C), and implantation conditions (random or channel implants). Upon postimplantation annealing at 800 °C for 600 s, in addition to the gettering at the projected range (Rp) region, the room temperature implanted samples also present Cu gettering in a region corresponding to the half of the projected range (Rp/2) depth. Also a threshold fluence (Ф≈7x1015 at/cm²) was determined for the appearance of the Rp/2 effect. In contrast, for the 350 °C implants, the Cu impurities are detected only close to the Rp region where the He induced cavities are formed. The gettering effect at Rp/2 region is discussed in terms of the cavity formation mechanisms and their influence on the point defect fluxes taking place during the thermal annealing.