Phosphorus diffusion in silicon; influence of annealing conditions

摘要

Phosphorus diffusion has been studied in both pure epitaxially grown silicon and Cz silicon, with a substantial amount of impurities like oxygen and carbon. Anneals have been performed in different atmospheres, N_2 and dry O_2, as well as in vacuum, at temperatures between 810 ― 1100℃. Diffusion coefficients extracted from these anneals show no difference for the P diffusion in the epitaxially grown or the Cz silicon. The diffusion coefficients follow an Arrhenius dependence with the activation energy E_a=2.74+-0.07 eV and a prefactor D_0 = (8+-5)x10~(-4) cm~2/s. These parameters differ considerably from the previously reported and widely accepted values (3.66 eV and 3.84 cm~2/s, respectively). However, vacuum anneals of the same samples result in values close to this 3.6 eV diffusion mode. Furthermore, control anneals of boron doped samples, with similar design as the phosphorus samples, suggest the same trend for boron diffusion in silicon ― lower versus higher values of activation energies for nitrogen and vacuum anneals, respectively. These results are discussed in terms of the concentration of Si self-interstitials mediating the diffusion of phosphorus and boron.