Negative annealing in silicon after the implantation of high-energy sodium ions

The implantation of sodium ions with an energy of 300 keV is carried out into high-resistivity p-Si. The annealing of defects at T (ann) = 350-450A degrees C and related activation of atoms (the latter occurs at the "tail" of atom distribution) are described by a first-order reaction. At T (ann) = 450-525A degrees C and irrespective of the ion dose, negative annealing is observed; this annealing is accompanied by an appreciable increase in the surface resistance rho (s) . According to estimations, the activation energy of this process amounts to similar to 2 eV. It is our opinion that the annealing is related to the precipitation of sodium donor atoms, which occurs at a depth exceeding by two-three times the projected range R (p) of ions. The annealing of defects at T (ann) = 525-700A degrees C, which leads to a further decrease in rho (s) , features an activation energy of similar to 2.1 eV. The hypothesis that the "tail" in the profiles of sodium atoms measured by secondary-ion mass spectroscopy is due to the diffusion of these atoms from the walls of the crater to its center is verified. It is shown that this process is not implemented since the profiles of sodium atoms measured at room temperature do not differ from those measured at-140A degrees C.