The last trap that form the percolation path - the stress voltage effect

Recently, (IRPS2003, p.432) the author observed that when the current surge at the moment of breakdown is largely suppressed, the probability of soft breakdown occurring is drastically reduced. Instead of soft breakdown, the neutral trap density continues to increase well beyond the "\´critical" level, leading to enhanced leakage. In a recent paper, (APL, vol.83, p.2400, (2003)), the author developed a model to explain the anomalous temperature effect on thin oxide breakdown. This model is used in here, to explain the current surge effect on breakdown. The model predicts that at low stress voltage, the reduced surge current, leads to a dramatic reduction in the probability of a permanent breakdown (soft or hard) when the percolation path is formed. The implication is that the breakdown lifetime projection from standard accelerated stress test is overly pessimistic.