Diffusion and activation of arsenic implanted at high temperature in silicon

Abstract

The aim of this work is to study the diffusion behavior and electrical activation of arsenic implanted at high temperatures in silicon. For this purpose, arsenic ions have been implanted into 〈100〉 oriented silicon at 180 keV to a dose of 1×10 15 cm −2 at temperatures in the range from 500 to 1000°C. The concentration profiles were measured by secondary ion mass spectrometry. They revealed that there is significant diffusion taking place during the implantation. The diffusion enhancement is considerable, compared to thermal diffusion. Comparisons of the depth distribution of residual defects as revealed by cross-sectional transmission electron microscopy with the concentration profiles were made. It is shown that the anomalous diffusion for implantation temperatures from 500 to 850°C markedly correlates with the depth distribution of the residual defects. For this temperature range, it is also found that the enhancement of arsenic diffusion increases with the implantation temperature, accompanying the decreased formation of the residual defects. However, for implantation temperatures above 850°C, the diffusion enhancement reduces with increasing temperature. This can be explained in terms of residual defects acting as sinks for point defects and the suggestion that point defects recombine faster at higher temperatures. The depth distributions of carrier concentration and mobility as examined by differential Hall measurements have shown that changes in carrier concentration and mobility also correlate with the depth distribution of the residual defects, and that the electrical activity increases with the implantation temperature in the temperature range from 500 to 1000°C.