HIGH-FIELD DYNAMIC STRESS OF THIN SIO2-FILMS

Thin-oxide MOS capacitors are subjected to unipolar and bipolar dynami c voltage stresses. The characteristic times of the measured current t ransients indicate that they are due to changes in the occupancy of in terface states. A reasonable picture is presented which invokes the re storation of equilibrium at the oxide/semiconductor interfaces, and th e stripping of electrons by Fowler-Nordheim tunnelling when the applie d field is very high. On the other hand, time-to-breakdown data show t hat, in agreement with the results of other authors, oxide reliability is considerably higher under high frequency bipolar stresses. A small er dependence of time-to-breakdown on the frequency of unipolar stress es is also found, and is qualitatively interpreted in terms of the ave rage energy required to breakdown.