Electrical property studies of oxygen in Czochralski-grown neutron-transmutation-doped silicon

Electically active oxygen-related donors can be formed in Czochralski (Cz) Si either during crystal growth or during subsequent heat treatment; conventional n- or p-type dopant carrier concentrations are altered if these oxygen donors are present. Neutron transmutation doping (NTD) has been used to introduce a uniform concentration of 31P in Si. However, oxygen donors can also be formed in NTD Cz Si during the process of annealing to remove NTD radiation damage. In the present experiments, the carrier concentration of Cz and NTD Cz Si samples was determined as a function of the initial dopant, oxygen, and 31P concentration before and after isothermal or isochronal annealing. It is shown that low temperature (350 to 5000C) heat treatment can introduce a significant oxygen donor concentration in Cz Si and in NTD Cz Si that contains radiation-induced lattice defects. Intermediate temperature (550 to 7500C) heat treatment, which is intended to remove oxygen donors or lattice defects, can introduce other oxygen donors; annealing above 7500C is required to remove any of these oxygen donors. Extended (20 h) high-temperature (1000 to 12000C) annealing can remove oxygen donors and lattice defects, but a significant concentration of oxygen donors can still be introduced by subsequent low temperature heat treatment. These results suggest that oxygen-related donor formation in NTD Cz Si at temperatures below 7500C may serve to mask any annealing study of lattice defects. It is concluded that annealing for 30 min at 7500C is sufficient to remove radiation damage in NTD Cz Si when the separate effects of oxygen donor formation are included