Density functional theory calculations were used to investigate the stress dependence of B and As diffusion including vacancy (V) and interstitial (I) mechanisms under arbitrary stress/strain states. The effects of stress upon I and V diffusion, with a resulting impact upon transient enhanced diffusion and coupled diffusion, were also analyzed. For B diffusion, which was primarily mediated by I, it was found that there was greatly enhanced diffusion under tensile stress. Due to the low symmetry of the calculated transition state, strongly anisotropic diffusion under anisotropic strain was predicted; with the strongest effects in the direction of the strain. This has a major impact on control of lateral junction abruptness as seen in 2-dimensional simulations. The predicted behavior was consistent with combined analysis of vertical diffusion under biaxial and hydrostatic stresses. In contrast, isotropic As diffusion was found for both I and V mediated processes. The As diffusivity was predicted to increase substantially under compressive strain, but to show little change under tensile strain, consistent with experimental observations.

Calculations of Effect of Anisotropic Stress/Strain on Dopant Diffusion in Silicon under Equilibrium and Non-Equilibrium Conditions. S.T.Dunham, M.Diebel, C.Ahn, C.L.Shih: Journal of Vacuum Science & Technology B, 2006, 24[1], 456-61