Effects of chemical surface treatments on the generation of AC surface photovoltages in n-type silicon wafers

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Abstract
An AC surface photovoltage (SPV) is observed in n-type silicon (Si) wafers treated with RCA solutions (alkaline and acid rinse) and aqueous hydrofluoric acid (HF) solution. The AC SPV increases with exposure time in air at room temperature, indicating that the negative charge increases. Aluminium (Al) in the native oxide contributes to this negative charge. The AC SPV saturates after (2-6)*103 min (1-4 days) and the saturation value depends on the concentration of Al, provided that the wafer surface is not strongly inverted. After HF dipping, relatively low AC SPVS appear after 20 days. This is because it takes time not only for the negative charge to arise at the surface. but also for the positive charge to decrease, as has been reported in p-type Si wafers.