Correlation of wearout and breakdown in sub-10 nm silicon oxide

Silicon oxide films less than 10-nm thick have been stressed at constant voltages from 2 V up to the breakdown voltage. The characteristics of the oxides were measured. The quasi-static C-V characteristics were used to determine the interface trap generation as a fluctuation of the stress voltage and polarity, the fluence through the oxide, and whether the stress was a DC stress or a series of pulses. The I-T dependence of the oxide during stress showed at RC time constant component, a resistive component, and an excess current component if the applied voltage was less than that needed for significant tunneling current. When tunneling currents became dominant both positive and negative charge trapping were observed. The number and energy distribution of interface traps generated per electron through the oxide was independent of stress polarity and decreased at lower stress voltages. The charge to breakdown was higher at lower stress voltages. The charge state of the interface traps after the stress was determined by the stress polarity. More interface traps were generated by pulsed stressing than by DC stressing.<>