Understanding Smart Sensors - Nomads.usp

Packaging, Testing, and Reliability Implications of Smarter Sensors 243Technical ReviewApplication, Environment,Definition of Failure,Lifetime Expectations,Sample SelectionTesting to Failure atVarious Stress Levels(D.O.E. Format)Analysis• Statistical Analysis• Lifetime Distributions• Physical AnalysisFailure Mode, Sites, andMechanism DeterminedModels EstablishedReliability (Time-Based)Figure 10.12 Physics of failure methodology.improve the strength of the die bond could limit device performance in otherareas, such as temperature coefficient of offset [16].10.5.2 Wafer-Level Sensor ReliabilityOne of the inherent advantages of semiconductor sensors is their capability ofintegrating the signal conditioning, temperature compensation, and essentiallyany aspect of semiconductor fabrication on the same silicon substrate as thesensor. That allows wafer-level reliability to be implemented. Test structures onthe wafer or monitor wafers allow evaluation of critical process steps as theyoccur and provide rapid feedback to detect and correct process errors. The costof testing at the wafer level is considerably less than testing at the completedassembly level. As shown in Table 10.2 [17], the cost of evaluating criticalprocess steps early in the wafer fabrication process provides a considerable costreduction over testing performed after the assembly process is complete. Thedata is a comparison of semiconductor process testing only. However, as sensortechnology advances, package approaches common in the semiconductor