Accurate Determination of the Intrinsic Diffusivities of Boron, Phosphorus, and Arsenic in Silicon: The Influence of SiO_2 Films

摘要

Accurate determination of the intrinsic diffusivities of boron (B), phosphorus (P), and arsenic (As) in silicon (Si) is reported. We show that the differences in the B, P, and As diffusivities reported in the previous works arise from whether SiO_2 films existed on the Si sample surfaces. Impurity diffusion near the Si surface without SiO_2 is affected by oxidation of Si even in the nominally inert atmosphere, which has unavoidable residual oxygen background due to the open furnace. On the other hand, a surface SiO_2 film of ～20 nm thickness prepared before the diffusion annealing is sufficient to block further oxidation of Si, i.e., truly intrinsic diffusivities of impurities have been obtained from samples having surface oxide layers.