DIFFUSION AND ACTIVATION OF ARSENIC IMPLANTED AT HIGH-TEMPERATURE IN SILICON

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 sil icon at 180 keV to a dose of 1 x 10(15) cm-2 at temperatures in the ra nge from 500 to 1000-degrees-C. The concentration profiles were measur ed by secondary ion mass spectrometry. They revealed that there is sig nificant diffusion taking place during the implantation. The diffusion enhancement is considerable, compared to thermal diffusion. Compariso ns of the depth distribution of residual defects as revealed by cross- sectional transmission electron microscopy with the concentration prof iles were made. It is shown that the anomalous diffusion for implantat ion temperatures from 500 to 850-degrees-C markedly correlates with th e depth distribution of the residual defects. For this temperature ran ge, it is also found that the enhancement of arsenic diffusion increas es with the implantation temperature, accompanying the decreased forma tion of the residual defects. However, for implantation temperatures a bove 850-degrees-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 reco mbine faster at higher temperatures. The depth distributions of carrie r concentration and mobility as examined by differential Hall measurem ents have shown that changes in carrier concentration and mobility als o correlate with the depth distribution of the residual defects, and t hat the electrical activity increases with the implantation temperatur e in the temperature range from 500 to 1000-degrees-C.