Analysis and mitigation or IR-Drop induced scan shift-errors
Stefan Holst, Eric W. Schneider, Koshi Kawagoe, Michael A. Kochte, Kohei Miyase, Hans-Joachim Wunderlich, Seiji Kajihara, Xiaoqing Wen · 2017
Excessive IR-drop during scan shift can cause localized IR-drop around clock buffers and introduce dynamic clock skew. Excessive clock skew at neighboring scan flip-flops results in hold or setup timing violations corrupting test stimuli or test responses during shifting. We introduce a new method to assess the risk of such test data corruption at each scan cycle and flip-flop. The most likely cases of test data corruption are mitigated in a non-intrusive way by selective test data manipulation and masking of affected responses. Evaluation results show the computational feasibility of our method for large benchmark circuits, and demonstrate that a few targeted pattern changes provide large potential gains in shift safety and test time with negligible cost in fault coverage.