V-Ramp test and gate oxide screening under the “lucky” defect model

The persistent (after exhaustive wafer cleaning) extrinsic breakdown distribution of thick gate oxides requires an early breakdown mechanism that goes beyond the popular local thinning model to explain. The success of the “Lucky” defect model in fulfilling this role deserves a further exploration of its implications. This work examines the implications of using the V-Ramp and the high-voltage screening methods to identify early failures. In this study, it is shown that the V-Ramp method fails to produce useful information about the oxide quality at operation voltages and that the high-field screening method fails to screen out early failures.