Implications QF a Model for Optimum Burn-In

The importance of burn-in as a screen to reduce failure rates (particularly early fails) of LSI/VLSI devices, and thereby achieve reliability objectives, is discussed. A mathematical model is described wich predicts the burn-in duration required to achieve any desired field reliability improvement. Based on a Weibull temporal fail distribution, the effects of voltage and temperature acceleration and escapes are included. Escapes -- those devices which are delivered incompletely burned-in or with undetected fails due either to inadequate stress or test procedures -- are shown to be the key factor limiting improvement in early failure rates (EFR). The model is compared to 1980 field data which reflect EFR sensitivity to escape levels. The usefulness of the model for examining the sensitivity of burn-in parameters is demonstrated. Finally, a strategy of In Situ test as a means of controlling escapes is discussed.