Mechanisms for interstitial-mediated transient enhanced diffusion of N-type dopants

As silicon transistors scale down, transient enhanced diffusion of n-type dopants has become a barrier toward achieving required junction depths for transistors. In this paper, we use density functional calculations to identify a pathway by which silicon interstitials (Si_i) mediate As and P diffusion. We show that As-Si_i and P-Si_i pairs in the neutral and negative charge states diffuse via a mechanism in which the dopant is bond-centered at energy minima and threefold coordinated at the high energy saddle point during dopant migration. For both As-Si_i and P-Si _i pairs, we conclude that neutral pairs will dominate under intrinsic conditions while the neutral and negatively charged pairs will both contribute under heavily doped extrinsic conditions.