Two-stage doping of silicon with phosphorus-32 and sulfur-32 isotopes

We describe a principally new approach to obtaining solid sources of sulfur for the two-stage diffusion doping of silicon, which eliminates the surface erosion of wafers. According to the proposed method, 32P radionuclide is diffused into a near-surface region of silicon in the first (introduction) stage and then converted into 32S isotope in the second state. It is shown that the samples of silicon doped by this method with 32S isotope contain deep levels with the ionization energies E c − 0.13 eV, E c − 0.25 eV, E c − 0.37 eV, and E c − 0.50 eV, which exhibit a donor character and are related to the sulfur impurity. It is established that the diffusion of 32S isotope into p-Si leads to a change in the type of conduction, while the diffusion of this isotope into n-Si decreases the resistivity of the initial material.

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