Studies of the interactions between (311) defects and type I and II dislocation loops in Si + implanted silicon

Abstract

Silicon wafers were implanted with Si + at doses of 2 × 10 14 and 1 × 10 15 /cm 2. Annealing treatments were done at temperatures between 700°C and 1000°C for times between 15 min and 16 h, both with and without an SiO 2 cap. Plan-view TEM micrographs were taken and the density of interstitials trapped in both the (311) defects and the type I and II perfect loops were measured. The results showed that for the 2 × 10 14 /cm 2 Si + dose, which is below the amorphization threshold, the dominant defect at 700°C is the (311) defect with a much smaller concentration of type I loops. The total trapped interstitial concentration in both kinds of defects was around 7 × 10 13 /cm 2 for 700°C 1 h anneals. The (311) defects begin dissolving after several hours at 700°C but their dissolution rate is slower than previously reported by Stolk et al. [MRS Symp. Proc. 354 (1995)] for lower dose (5 × 10 13 /cm 2) implants. It is not believed that this slower dissolution rate is due to the increased dose. The reduced dissolution rate does not change with capping and may be due to a difference in furnace calibration methods. The type I loops show some growth during the (311) dissolution but quantitatively less than half of the released interstitials appear to be trapped by the type I loops. For the 1 × 10 15 /cm 2 sample amorphization occurs and both type II (end of range) loops and (311) defects are observed for 700°C anneals. The total number of trapped interstitials for 700°C 1 h anneals is also around 7 × 10 13 /cm 2. However, the ratio of (311) to loops has switched such that the dominant defect is the type II loop. Upon annealing, the (311) defects again show a reduced dissolution rate and the type II loops are in the growth regine. Increasing the anneal temperature to 800°C results in further growth of the type II loops and all of the (311) defects have either dissolved or unfaulted. The growth of the type II loops appears to be greater than can be quantitatively accounted for by the (311) defects. In addition there is a high level of strain in the lattice that cannot be accounted for by the (311) defects. Both of these results imply there may be an additional source of interstitials besides the (311) defects for amorphizing implants.