Determination of Surface Charge and Interface Trap Densities in Naturally Oxidized n-Type Si wafers Using ae Surface Photovoltages

An ac surface photovoltage method was applied in order to estimate the fixed oxide charge density in naturally oxidized n-type Si wafers. Three n-type Si wafers (100-mm diameter, 540-µm thick and a resistivity of 1.1 mΩ·m) were used after forming 2.4-nm oxide layers on their surfaces as the result of an alkaline rinse treatment. The ac surface photovoltages in the frequency range of 1 Hz to 10 kHz were analyzed using the half-sided junction model previously reported. The photon energy of the probing beam was 2.23 eV. The surface potential, fixed oxide charge and interface trap densities were determined to be –0.38 V, –0.93 mC·m-2 and 5×1015m-2·eV-1, respectively.