LOW-LEVEL LEAKAGE CURRENTS IN THIN SILICON-OXIDE FILMS

The low-level leakage currents in thin silicon oxide films were measured before and after the oxides had been stressed at high voltages. Four components of current were identified. These components were the tunneling cuff ent, the capacitive current associated with the measurement sweep rate, a negative differential current associated with the voltage sweep through the changing oxide C-V characteristic, and an excess current that occurred after the high-voltage stress. The excess current was due to the charging and discharging of traps generated inside of the oxide by the high-voltage stress. The excess current was proportional to the number of traps generated in the oxide. The magnitude of the excess current could be changed by changes in the measurement procedures due to the charging and discharging of traps. A major portion of the stress-generated excess low-level leakage current may not be a current that flowed through the oxide, but may be a trap charging/discharging current. This paper will concentrate on describing the low-level pretunneling leakage currents and the measurement techniques needed to determine the properties of the excess leakage currents associated with the traps generated inside of the oxide.