Field-induced positive oxide charge in radiation-damaged oxide layers on n-type silicon wafers

The polarity of the oxide charge in a thermally wet-oxidized and radiation-damaged n-type silicon wafer was determined by the conventional capacitance-voltage (C-V) method and an ac surface photovoltage (SPV) technique. The C-V method, which uses a mercury probe as the metal electrode, results in a positive sign, while the SPV technique gives a negative one for the radiation-damaged region of the oxide layer. The two conflicting results suggest that the electric field due to the metal probe has changed the oxide-charge state underneath the probe.