Effectiveness Improvement of ECR Tests

Energy Consumption Ratio (ECR) test, a current-based test, has shown its ability to reduce the impact of process variations and detect hard-to-detect faults. The effectiveness of ECR tests may be degraded by a large number of normal transitions in a circuit, which may bury the fault impact on the overall current. For deterministic ECRs, the fault-oriented ECR tests are generated with an algorithm to minimize the number of normal transitions not related with the sensitizable path of the target faults. For generalized ECRs, however, the test patterns are generic without targeting any specific faults and therefore may cause a significant amount of transient activities in a CUT. This issue is addressed in this paper by utilizing a DFT technique, multiple scan chain design. This technique virtually partitions the circuit into several sections, so that the transitions in each section can be much less compared with those in the whole circuit. The fault impact can be more significant with fewer transitions in the circuit, which hence increases the ECR test effectiveness. The anti-process-variation property of the ECR metric is also demonstrated through a negligible lotto-lot shift. Finally, the effectiveness of ECR tests with different thresholds is compared with existing traditional tests.