Study of the long term stability of the effective concentration of ionized space charges (Neff) of neutron irradiated silicon detectors fabricated by various thermal oxidation processes

An experimental study of the reverse annealing of the effective concentration of ionized space charges (N_eff, also called effective doping or impurity concentration) of neutron irradiated high resistivity silicon detectors fabricated on wafers with various thermal oxides has been conducted at room temperature (RT) and elevated temperature (ET). Various thermal oxidations with temperatures ranging from 975°C to 1200°C with and without trichlorethane (TCA), which result in different concentrations of oxygen and carbon impurities, have been used. It has been found that, the RT annealing of the N_eff is hindered initially (t<42 days after the radiation) for detectors made on the oxides with high carbon concentrations, and there was no carbon effect on the long term (t>42 days after the radiation) N_eff reverse annealing. No apparent effect of oxygen on the N_eff stability has been observed at RT. At elevated temperature (80°C), no significant difference in annealing behavior has been found for detectors fabricated on silicon wafers with various thermal oxides. It is apparent that for the initial stages (first and or second) of N_eff reverse annealing, there may be no dependence on the oxygen and carbon concentrations