Boron diffusion was investigated in detail by monitoring B-sharp concentration profiles embedded in iso-concentration doping backgrounds. Atomistic diffusion parameters such as the kick-out rate, mean-free path of mobile species and diffusivity were evaluated experimentally as a function of temperature and doping level (p or n type). This permitted a quantitative determination to be made of the physical phenomena involved in B diffusion. It was found that negatively-charged substitutional B diffused via interaction with neutral or doubly positively charged self-interstitials. The BI complex, formed after interaction, diffused mainly in a neutral state and partially in a singly negatively charged state. The former contributed about 10% to the full diffusion under intrinsic conditions at 700C, while it played a significant role in high n- co-doping regimes. Also, n co-doping with As or P induced Coulomb pairing between the various charge states of the dopants and reduced diffusion. The pairing effect was broken up by the effect of BI− diffusion, and the pairing energies were determined for both As and P.

Boron Diffusion in Extrinsically Doped Crystalline Silicon. D.De Salvador, E.Napolitani, G.Bisognin, M.Pesce, A.Carnera: Physical Review B, 2010, 81[4], 045209