Optimal Accelerated Test Framework for Time-Dependent Dielectric Breakdown Lifetime Parameter Estimation

A framework is presented to identify an optimal accelerated test region and accelerated test conditions for the accelerated test of logic circuits for time-dependent dielectric breakdown (TDDB). Both gate-oxide breakdown and middle-of-line (MOL) TDDB are investigated. Separate test regions are identified for each wearout mechanism. Two digital circuits, an 8-bit fast Fourier transform (FFT) circuit and a Leon3 microprocessor are used to demonstrate the capability of the framework. The lifetimes of standard cells are combined to compute the circuit lifetime, by combining the Weibull distributions that characterize the lifetime distribution of each of the standard cells. The errors in estimating wearout parameters consist of two parts: the error in estimating the wearout parameters at accelerated test conditions and the forecasting accuracy at use conditions. By estimating the errors in wearout parameters at accelerated test conditions, the optimal accelerated test region is found by determining the test conditions producing a minimal error. Test conditions are selected by minimizing the error at use conditions. Given a forecasting error target, the required sample size at each test condition is found. This work also considers the impact of variation in circuit size, type, and process parameters on the selection of optimal test conditions.