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, 32 P radionuclide is diffused into a near-surface region of silicon in the first (introduction) stage and then converted into 32 S isotope in the second state. It is shown that the samples of silicon doped by this method with 32 S 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 32 S 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.