IMPURITY GETTERING TO SECONDARY DEFECTS CREATED BY MEV ION-IMPLANTATION IN SILICON

Impurities in MeV-implanted and annealed silicon may be trapped at int erstitial defects near the projected ion range, R-p, and also at vacan cy-related defects at approximately R-p/2. We have investigated the te mperature dependence of impurity trapping at these secondary defects, which were pn formed by annealing at 900 degrees C, The binding energi es of Fe, Ni, and Cu are greater at the vacancy-related defects than a t extrinsic dislocation loops. During subsequent processing at tempera tures up to 900 degrees C, the amount of these impurities trapped at R -p/2 increases with decreasing temperature while the amount trapped at R-p decreases, with most of the trapped metals located at R-p/2 in sa mples processed at temperatures less than or similar to 700 degrees C, However, intrinsic oxygen is trapped at both types of defects; this a ppears to have little effect on the trapping of metallic impurities at extrinsic dislocations, but may inhibit or completely suppress the tr apping at vacancy-related defects. (C) 1998 American Institute of Phys ics. [S0021-8979(98)00517-9].