Electron beam doping by superdiffusion in unirradiated regions (X < 300 Å) of semiconductors at room temperature

Electron beam doping processes in the damageless region and at room temperature were investigated before annealing. In the three-layer system of layer 3/layer 2/layer 1, the impurity sheet (layer 2) was sandwiched between two semiconductor wafers. The surface of layer 3 was irradiated with electron beams of 750 keV and 7 MeV. Interstitials of displaced atoms in the overlayer, which were introduced by irradiation, migrated to the surface of the semiconductors. These interstitials diffused rapidly at the surface with a very large surface diffusivity of ∼10 -5 cm 2 · s -1 . The diffusion process was observed using an atomic force microscope (AFM). Impurity concentrations in the surface layer during irradiation were found to be on the order of matrix atom concentration. Electron irradiation produced a number of self-interstitials that migrated with large surface diffusivities at the surface. Diffusion was enhanced due to the kick-out mechanism at the interface of the system and in the depth direction of the semiconductors.