1/f noise reduction in PMOSFETs by an additional preoxidation cleaning with an ammonia hydrogen peroxide mixture

1/f noise magnitude in a 15 μm×0.5 μm PMOSFET was remarkably reduced by simply adding a cleaning step using an ammonia hydrogen peroxide mixture (APM) prior to gate oxidation. Gate input-referred noise level for APM-finished PMOSFETs at f=10 Hz was around -128 dBV
²
/Hz whereas for standard, HF-finished devices, the level was around -114 dBV
²
/Hz. Flat-band voltages (V/sub FB/s) determined by a capacitance-voltage (C-V) measurement were -0.19 V for an APM-finished PMOS and -0.34 V for a HF-finished PMOS. Based on the V/sub FB/ values, interface state densities were determined to be N/sub it/=3.02×10/sup 11/ cm/sup -2/ for APM-finished PMOS and N/sub it/=6.47×10/sup 11/ cm/sup -2/ for HF-finished PMOS. Lower interface state density obtained by the APM preoxidation cleaning is consistent with the remarkable reduction in the 1/f noise magnitude.