Defects in oxidized p-type Si wafers observed by surface photovoltage spectroscopy

Surface photovoltage spectroscopy (SPV) is widely used for semiconductor characterization in modern microelectronics. In the present study we report the results of a comprehensive SPV analysis of oxidized n- and p-type Czochralski (Cz) Si wafers with an oxygen concentration of about 5-7×1017 cm-3. We demonstrate that the oxidation of the wafers with different H2/O2 ratios can significantly influence the diffusion length of minority carriers in p-type Si. We explain this effect by the formation of OH-related defects which are strong recombination centers in such wafers. In addition, a significant degradation of the diffusion length of minority carriers was observed in oxidized p-type Si wafers after annealing at 90 °C and a subsequent illumination at room temperature. This degradation was found to be independent on oxide growth conditions and it was not observed in n-type wafers. We correlate this degradation with the presence of low concentrations of interstitial Fe (<1011 cm-3) in some wafers and with BO-related defects in some other wafers. Surface photovoltage spectroscopy (SPV) is widely used for semiconductor characterization in modern microelectronics. In the present study we report the results of a comprehensive SPV analysis of oxidized n- and p-type Czochralski (Cz) Si wafers with an oxygen concentration of about 5-7×1017 cm-3. We demonstrate that the oxidation of the wafers with different H2/O2 ratios can significantly influence the diffusion length of minority carriers in p-type Si. We explain this effect by the formation of OH-related defects which are strong recombination centers in such wafers. In addition, a significant degradation of the diffusion length of minority carriers was observed in oxidized p-type Si wafers after annealing at 90 °C and a subsequent illumination at room temperature. This degradation was found to be independent on oxide growth conditions and it was not observed in n-type wafers. We correlate this degradation with the presence of low concentrations of interstitial Fe (<1011 cm-3) in some wafers and with BO-related defects in some other wafers.