On Guaranteeing Capture Safety in At-Speed Scan Testing with Broadcast-Scan-Based Test Compression

Capture safety has become a major concern in at-speed scan testing since strong power supply noise caused by excessive launch switching activity (LSA) at transition launching in an at-speed test cycle often results in severe timing-failure-induced yield loss. Recently, a basic RM (rescue-&-mask) test generation scheme was proposed for guaranteeing capture safety rather than merely reducing LSA to some extent. This paper extends the basic RM scheme to broadcast-scan-based test compression by uniquely solving two test-compression-induced problems, namely (1) input X-bit insufficiency (i.e., fewer input X-bits are available for LSA reduction due to test compression) and (2) output X-bit impact (i.e., output X-bits may reduce fault coverage due to test response compaction). This leads to the broadcast-RM (broadcast-scan-based rescue-&-mask) test generation scheme. Evaluations on large benchmark circuits and an industrial circuit of about 1M gates clearly demonstrate that this novel scheme can indeed guarantee capture safety in at-speed scan testing with broadcast-scan-based test compression while minimizing its impact on both test quality and test costs.2013 26th International Conference on VLSI Design, 5-10 January 2013, Pune, Indi

Logic/Clock-Path-Aware At-Speed Scan Test Generation for Avoiding False Capture Failures and Reducing Clock Stretch

IR-drop induced by launch switching activity (LSA) in capture mode during at-speed scan testing increases delay along not only logic paths (LPs) but also clock paths (Cps). Excessive extra delay along LPs compromises test yields due to false capture failures, while excessive extra delay along CPs compromises test quality due to test clock stretch. This paper is the first to mitigate the impact of LSA on both LPs and CPs with a novel LCPA (Logic/Clock Path-Aware) at-speed scan test generation scheme, featuring (1) a new metric for assessing the risk of false capture failures based on the amount of LSA around both LPs and CPs, (2) a procedure for avoiding false capture failures by reducing LSA around LPs or masking uncertain test responses, and (3) a procedure for reducing test clock stretch by reducing LSA around CPs. Experimental results demonstrate the effectiveness of the LCPA scheme in improving test yields and test quality.2015 IEEE 24th Asian Test Symposium (ATS), 22-25 November 2015, Mumbai, Indi

On Guaranteeing Capture Safety in At-Speed Scan Testing with Broadcast-Scan-Based Test Compression

Capture safety has become a major concern in at-speed scan testing since strong power supply noise caused by excessive launch switching activity (LSA) at transition launching in an at-speed test cycle often results in severe timing-failure-induced yield loss. Recently, a basic RM (rescue-&-mask) test generation scheme was proposed for guaranteeing capture safety rather than merely reducing LSA to some extent. This paper extends the basic RM scheme to broadcast-scan-based test compression by uniquely solving two test-compression-induced problems, namely (1) input X-bit insufficiency (i.e., fewer input X-bits are available for LSA reduction due to test compression) and (2) output X-bit impact (i.e., output X-bits may reduce fault coverage due to test response compaction). This leads to the broadcast-RM (broadcast-scan-based rescue-&-mask) test generation scheme. Evaluations on large benchmark circuits and an industrial circuit of about 1M gates clearly demonstrate that this novel scheme can indeed guarantee capture safety in at-speed scan testing with broadcast-scan-based test compression while minimizing its impact on both test quality and test costs.2013 26th International Conference on VLSI Design, 5-10 January 2013, Pune, Indi