BIPOLAR STRESSING, BREAKDOWN, AND TRAP GENERATION IN THIN SILICON-OXIDES

Thin silicon oxide films were stressed with bipolar pulses in which th e magnitudes of both the positive and negative pulses were independent ly varied. The time-to-breakdown, the charge-to-breakdown, and the num ber of traps generated inside of the oxides during the stresses were m easured and compared with oxides that had been stressed with unipolar pulses or stressed with constant dc voltages. For the bipolar stresses it was found that the time-to-breakdown, the charge-to-breakdown, and the number of traps generated inside of the oxide all increased as th e magnitude of the opposite polarity, nonstressing pulse was increased , until the opposite polarity pulse became large enough to become the stressing pulse. The time-to-breakdown reached a maximum when the magn itude of the stressing pulse was approximately 1 V larger than the mag nitude of the nonstressing pulse. The model that was used to explain t hese increases involved generation of traps inside of the oxide and th e lack of spatial correlation between the traps generated by injection from one interface with the traps generated by injection from the oth er interface.