Correlation between Flatband Voltage Shift in MOS Capacitors and Endurance Degradation of EEPROM Cells

Charge trapping in thin Injection oxides used in EEPROMs is studied as a function of charge injected into the oxide. In MOS capacitors, pulsed alternating current injection is used to simulate the operation of EEPROM. The resulting shifts of flatband voltage are correlated with the shifts of threshold voltage in the WRITTEN and ERASED states in EEPROM cells. Positive charge generation depends more than negative trapping on the negative field strength and is found to vary with the stress history of the oxide.