The statistical distribution of breakdown from multiple breakdown events in one sample

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Abstract
Several breakdown events have been observed in ultrathin SiO2 layers when subjected to constant-voltage stress. It has been shown that the I(V) and I(t) characteristics can be understood assuming that the sample is formed by a great number of independent capacitors (spots) connected in parallel. Each breakdown event corresponds to the dielectric failure of one of these spots. The failure rate of the spots is related to the failure rate of the samples by the well known area effect of the breakdown statistical distribution. It is demonstrated that the failure rate of the samples is related to the number of broken spots and that it can be directly obtained from the evolution of the current with time. So, the statistical distribution of the first breakdown of a set of capacitors can be obtained by provoking multiple breakdown events in only one sample during a constant-voltage stress. Experimental results are presented which demonstrate that this is a very powerful alternative technique to measure experimentally the statistical distribution of breakdown in wearout tests.