Error evaluation of C-V characteristic measurements in ultra-thin gate dielectrics

The errors of Capacitance-Voltage (C-V) characteristic measurements for ultra-thin gate dielectrics in MOS capacitor were studied by I-V method. It was found that there are two reasons for the errors at low measurement frequencies: (1) the deviation of the phase angle of measured impedance, which causes apparent "Negative capacitance" that is inversely proportional to the measurement frequency. (2) AC-response in non-Ohmic conducting materials that form MOS capacitors, which may result in "Negative" or "Excess" capacitance. It was also found that the errors due to phase angle inaccuracy could be eliminated both by the phase rotation correction of the impedance and by measurements at higher frequencies. The errors due to non-Ohmic conduction should be avoided by measurements of MOS-capacitors with small gate areas and low parasitic AC-impedance.