Low Overhead Partial Enhanced Scan Technique for Compact and High Fault Coverage Transition Delay Test Patterns

This paper presents a scan-based DFT technique that uses limited number of enhanced scan cells to reduce volume of delay test patterns and improve delay fault coverage. The proposed method controls a small number of enhanced scan cells by the skewed-load approach and the rest of scan cells by the broadside approach. Inserting enhanced scan cells reduces test data volume and ATPG run time and improves delay fault coverage. Hardware overhead for the proposed method is very low. The scan inputs where enhanced scan cells are inserted are selected by gain functions, which consist of controllability costs and usefulness measures. A regular ATPG can be used to generate transition delay test patterns for the proposed method. Experimental results show that test data volume is reduced by up to 65% and fault coverage is improved by up to about 6%.