The Estimation of the Lifetime Variation for Power Devices

The paper proposes a methodology for estimation of the variation of power devices lifetime using data from different stages of development and tests. In the characterization process of power devices, the estimation of the minimum lifetime is not a simple task, especially when each stress-test lasts weeks and only a few lifetime measurements are available. In this case, the estimation of the minimum lifetime based only on the distribution of measured data is not effective, so very large safety margins are taken for guaranteeing of the lifetime parameters. The proposed methodology overcomes the problem of limited available data. It determines, in an automatic way, the most relevant electrical parameters (measured before the stress-test) which influence the lifetime spread and then, uses their distributions from back-end stage, where thousands of devices are measured, to predict the distribution of the lifetime and, out of it, the minimum lifetime. Thus, by using the initial electrical parameters in the estimation of the lifetime spread, the variation of the manufacturing process is indirectly taken into account. The validation of the lifetime variation model, with leave-one-out method, shows a maximum relative error of 25%. With the proposed methodology, based on data from different stages of development, the minimum lifetime of power devices can be more accurately predicted, even when only a few lifetime measurements are available.