LOG-NORMAL DISTRIBUTION OF ELECTROMIGRATION LIFETIMES

It has been shown that a normal temperature distribution within a sample set can produce a log-normal failure rate in electromigration experiments if it is assumed that the equation tf=Aj-n exp(Ef/kT) holds for individual stripe lifetimes. It has also been pointed out that if σ's determined under accelerated-stress conditions are used to predict failure under normal-use conditions, incorrect failure rates may result. It has also been demonstrated that most of the σ's observed in accelerated tests can be attributed to variations in temperature.