Test Pattern Ordering and Selection for High Quality Test Set under Constraints

Abstract

SUMMARY Nano-scale VLSI design is facing the problems of in-creased test data volume. Small delay defects are becoming possiblesources of test escapes, and high delay test quality and therefore a greatervolume of test data are required. The increased test data volume requiresmore tester memory and test application time, and both result in test costinflation. Test patternorderinggivesa practical solution toreducetest cost,wheretestpatternsareorderedsothatmoredefectscanbedetectedasearlyas possible. In this paper, we propose a test pattern ordering method basedonSDQL(StatisticalDelayQualityLevel),whichisameasureofdelaytestquality considering small delay defects. Our proposed method orders testpatternsso that SDQL shrinks fast, which means moredelaydefects can bedetected as early as possible. The proposed method efficiently orders testpatterns with minimal usage of time-consuming timing-aware fault simu-lation. Experimental results demonstrate that our method can obtain testpattern ordering within a reasonable time, and also suggest how to preparetest sets suitable as inputs of test pattern ordering.