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Advantages of the building-in reliabiity (BIR) methodology for semiconductor manufacturing are identified and discussed.

The isothermal electromigration (EM) test at wafer level can greatly reduce the test time from months to minutes. This plausible feature makes inline reliability monitor a promising approach to enhance product reliability. Although most wafer-level reliability (WLR) tests are applied for process monitors and comparisons, their applicability for qualification will be justified. The correlation between package-level reliability (PLR) and the isothermal EM is necessary and is discussed in this paper. Besides failure analysis, the 95% confidence interval of activation energy is constructed. Since the sizes of voids formed at isothermal EM are much smaller than those at PLR EM tests, the failure criterion should be changed (i.e., using a smaller [DELTA] R). Issues for better test structure designs are described and verified. Generally, the straight-line test structure with four pads is recommended for the isothermal EM tests because of the uniform temperature profile. An extensive example is provided to illustrate the procedures on isothermal EM tests for WLR control. In the example, we propose using [t.sub.50] for routine Cpk review and the slope of the fitting line to monitor the degradation. The spec limits can be obtained based on customers' or internal reliability goals. Index Terms--Black model, confidence interval, control limit, Cpk, Ea, EM, FA, isothermal, PLR, WLR, WLRC.

System burn-in can get rid of more residual defects than component and subsystem burn-ins because incompatibility exists not only among components, but also among different subsystems and at the system level. There are two major disadvantages for performing the system burn-in: the high burn-in cost and the complicated failure rate function. This paper proposes a nonparametric approach to estimate the optimal system burn-in time. The Anderson-Darling statistic is used to check the constant failure rate (CFR), and the pool-adjacent-violator (PAV) algorithm is applied to 'unimodalize' the failure rate curve. Given experimental data, the system burn-in time can be determined easily without going through complex parameter estimation and curve fittings.

A nonlinear model has been developed to find optimal burn-in times for all levels and optimal redundancy for every subsystem. It shows that reliability of the target system can be achieved by lowering the incompatibility or component hazards rates. The system reliability is susceptible to the compatibility level of the initial system. Burn-in times increase due to decreases in burn-in cost because it is more useful to burn-in items than to raise the subsystem numbers.