The effects of the recoil-implanted oxygen in Si on the electrical activation of As after through-oxide implantation

Abstract

The effects of the recoil‐implanted oxygen resulting from high‐dose As implantations into (111) Si through a thin SiO₂ film on the electrical activation have been studied in the dose range 10¹⁵–10¹⁶ ions/cm². The concentration profiles of total electrically active As and recoil‐implanted oxygen have been measured and compared with each other. It was found that the electrically active As profiles derived from the measured resistivity by assuming published data of mobility which are characteristic of defect‐free silicon show an apparent fall‐off in the surface region for the implantation with doses above 5×10¹⁵ ions/cm². It is shown that the apparent fall‐off in the profiles is caused by both the reduction of the mobility and net carrier concentration in the case of 800 °C anneal, while the former is the main cause in case of 1000 °C anneal. By comparing the mobility profiles with the measured concentration profiles of the recoil‐implanted oxygen, the marked reduction of the mobility is shown to occur in the region where the oxygen concentration exceeds ∼10²⁰/cm³. From the analysis of the depth distribution of the defects remaining in Si after annealing, it was demonstrated that the region is confined to the thin layer where the anomalous high‐density defects are present. For the As implantation with a dose less than 10¹⁵ ions/cm², however, the recoil‐implanted oxygen is likely to have little influence on the electrical activation of the implanted As in the temperature range studied.