Theoretical study of hydrogen impact on concentration of intrinsic point defects during Czochralski Si crystal growth

Abstract

Control of intrinsic point defects (vacancy V and interstitial Si I) at the atomic level is required for Si substrates to satisfy the performance demands of the latest semiconductor devices. Sugimura et al. (2014) recently reported that doping hydrogen (H) atoms during Czochralski Si crystal growth affects the point defect behavior in two ways: (i) Si crystal becomes more V rich and (ii) the formation of dislocation clusters is suppressed. The finding of (ii) suggests that H-doping is a promising technique for the mass production of Si substrates used for power devices, among other applications. However, the effect of H-doping on point defect behavior during Si crystal growth is not yet fully understood. The purpose of the present study is to clarify the finding of (i). We performed first principles calculation of the formation energy and formation (vibration) entropy of V and I in the area influenced by the H atom in supercells composed of 64 and 216 Si atoms and then obtained the concentration of point defects incorporated at the melt/solid interface on the basis of the results. Our main findings are as follows. (1) There are three structures of hydrogen-vacancy complex (H-V) where the V formation energy remarkably decreases and four structures of hydrogen-interstitial Si complex (H-I) where the I formation energy remarkably decreases. (2) The H impact on V concentration is larger than that on I concentration and becomes apparent when H concentration is higher than 1015/cm3. (3) The experimental finding of H impact on the concentration of intrinsic point defects is explained quantitatively.