Radiation damage evolution and its relation with dopant distribution during self-annealing implantation of As in silicon

Abstract

The evolution of radiation damage and of dopant profiles in Si samples subjected to self-annealing implantation with 160 keV As+ ions, under various transient heating conditions, depending on the beam current density, has been investigated. For temperatures in excess of 880 °C, the formation of voids is evidenced by Transmission Electron Microscopy observations. They are located in a layer extending from the surface over a depth of about 0.8 of the ion projected range, Rp (≃110 nm), while extended interstitial-type defects are observed in the region below. With increasing temperature (due to increasing beam power density and/or irradiation time), voids tend to anneal in the near surface region, while they survive and grow in a region about 40 nm thick, centered at a depth of about 50 nm, where an anomalous peak in the dopant profile is developed. The annealing of the extended interstitial-type defects at depths ≥Rp, which becomes appreciable for T ≥ 1050 °C, is coupled to a large enhancement of dopant diffusivity in the same region. It is argued that the local vacancy supersaturation, which leads to void formation, and the corresponding interstitial excess in the deeper region, which leads to extended defect formation, are a natural consequence of the collision kinetics of the displacement process, as suggested by Monte Carlo simulations reported in the literature. The evolution of damage and the anomalies in the redistribution of dopant, observed by increasing the temperature, are described as the result of the increase in the population of mobile point defects and of their influence on the mechanism of As diffusion in the different regions of the implanted layer.