Abstract
Scan-based structural testing methods have seen numerous inventions in scan compression techniques to reduce TDV (test data volume) and TAT (test application time). Compression techniques lead to test coverage (TC) loss and test patterns count (TPC) inflation when higher compression ratio is targeted. This happens because of the correlation issues introduced by these techniques. To overcome this issue, we propose a new hybrid scan compression technique, the aggressive exclusion (AE) of scan cells from compression for increasing overall TC and reduce TPC. This is achieved by excluding scan cells which contribute to 12% to 43% of overall care bits from compression architecture, placing them in multiple scan chains with dedicated scan-data-in and scan-data-out ports. The selection of scan cells to be excluded from the compression technique is done based on a detailed analysis of the last 95% of the patterns from a pattern set to reduce correlations. Results show improvements in TC of up to 1.33%, and reductions in TPC of up to 77.13%.
Highlights
Scan compression technology is improving with technology nodes shrinking from μm to 5 nm and continuing to shrink
The aggressive exclusion (AE) method motto is to increase test coverage (TC) and reduce test patterns count (TPC) by excluding scan cells which contribute to higher correlations in the compression architecture, stitching them in separate scan chains with dedicated assignment of scan-data-input and scan-data-output ports
The improvement in TPC ‘TPCimpr’ when both compression technique and the AE method are compared as TPCimpr = 100 × TPCae/TPCcs where TPCcs and TPCae are test patterns count achieved by the compression technique and the AE
Summary
Scan compression technology is improving with technology nodes shrinking from μm to 5 nm and continuing to shrink. To overcome the drawbacks of scan mode testing, scan chain partitioning is proposed; one such method is described in [1] This is a framework-based multiple scan path [2,3] having unique scan-data-input and scan-data-output. The disadvantage of this method is its need of many scan-data-input. The disadvantage of this method is its need of many scan-data-input and scan-data-output ports. The same ATE channel broadcasts test data into multiple internal scan chains
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