A comparative study of SILC transient characteristics and mechanisms in FN stressed and hot hole stressed tunnel oxides

High field stressing during program/erase cycles in flash EEPROM operation can lead to a significant increase in low-level leakage current in tunnel oxides. Stress induced leakage current (SILC) has received a lot of attention recently due to its significance to the data retention and endurance characteristics of flash memory cells. In this paper, the mechanisms and transient characteristics of hot hole stress and FN stress induced excess leakage currents in tunnel oxides are investigated. Hot hole SILC is found to have a more pronounced transient effect. The transient is attributed to positive oxide charge detrapping and thus annihilation of positive charge-assisted tunneling current. The positive charge assisted tunneling current can be annealed by substrate hot electron injection. The DC and transient components in FN SILC are also discussed.