INFLUENCE OF POSTIMPLANTATION ANNEALING ON ELECTRICAL-PROPERTIES OF FLUORINE-IMPLANTED SILICON LAYERS

Silicon with n- and p-type conduction was implanted with 200-keV F+ ions in doses of (1-8) X 10(13) cm-2 and with 300-keV ions in a dose of 3 X 10(15) cm-2. Implantation was followed by annealing in an argon atmosphere at temperatures of 400-1100-degrees-C. Such post-implantation annealing altered the density and charge state of the carriers. Additional carriers appeared in the implanted region and in a region exceeding greatly the depth of the implanted layer. It was found that implantation of F+ in silicon of either type of conduction and subsequent annealing produced electrically active complexes whose nature and concentration depend strongly on the implantation doses and on the annealing temperature. The profiles of the carrier density, which coincide with the distribution of flourine, and the investigated dose dependence indicate that additional carriers are formed because of ionization of the complexes containing fluorine. The results show that the density of these additional carriers does not exceed a few percent of the bulk concentration of fluorine.