Low temperature iron gettering by grown-in defects in p-type Czochralski silicon

摘要

Low temperature iron gettering in as-grown boron doped Czochralski silicon (Cz-Si) at temperatures between 220 and 500 ℃ is studied using microwave-photoconductive decay based minority carrier lifetime measurements. Scanning infrared microscopy technique is used to study the defect density/size distribution in the samples before and after anneal. It is found that the decrease of interstitial iron (Fe_i) concentration shows a double exponential dependence on annealing time at all temperatures. This suggests the existence of two sinks for Fe_i. Meanwhile, the observed bulk defect densities and sizes in contaminated and as-grown samples are nearly the same, implying that the grown-in defects could be the gettering centers in this process. The results are important for understanding and controlling low temperature Fe_i gettering during processing of Cz-Si based devices.