Ionization, thermal, and flux dependences of implantation disorder in silicon

Abstract

Proton channeling effect measurements were used to study the implantation lattice disorder in silicon as a function of ion flux (dose-rate), fluence, implant temperature, ion mass, and the presence of ionizing radiation. For both O⁺ and Sb⁺ implantation at 87°K the lattice disorder production is the same for equal total energy into atomic processes/cm³ at a fixed rate of energy into atomic processes/cm³-sec. The disorder production for both light (O⁺)and heavy (Sb⁺) ions exhibits a flux dependence at low temperatures and at room temperature. At low temperatures an increase in disorder is observed for increasing flux at constant fluences; however, for low fluence Sb implantation at 300°K, lower disorder is observed with increasing flux. The lattice disorder increases for all ions with decreasing implant temperature from 300°K down to temperatures as low as 38°K, but the variation with temperature is greater for lighter ions. The stimulation of lattice disorder annealing (typically ≍ 10 per cent) by ion beams was observed between 87 and 360°K. The results of disorder production and lattice reordering are interpreted in terms of the energy deposited into atomic and electronic processes, and previously observed lattice defect properties in Si. Ionization due to the energy deposited into electronic processes by the ions is believed to stimulate the anneal of defects from a disorder cluster in a manner similar to the charge state and injection-stimulated vacancy annealing previously observed for neutron and electron damage in Si. We suggest that ionization-stimulation of the lattice disorder annealing during implantation is responsible for the large differences observed in Si between the implant temperature and anneal temperature curves.