EffiTest2: Efficient Delay Test and Prediction for Post-Silicon Clock Skew Configuration under Process Variations

At nanometer manufacturing technology nodes, process variations affect circuit performance significantly. This trend leads to a large timing margin and thus overdesign in the traditional worst-case circuit design flow. To combat this pessimism, post-silicon clock tuning buffers can be deployed to balance timing slacks of consecutive combinational paths in individual chips by tuning clock skews after manufacturing. A challenge of this method is that path delays of each chip with timing failures should be measured to gather the information for clock skew configuration. However, current methods for delay measurement rely on path-wise frequency stepping, which requires much time from expensive testers. In this paper, we propose an efficient delay test framework (EffiTest2) to solve the post-silicon testing problem by testing only representative paths with delay alignment using the already-existing tunable buffers in the circuit. Experimental results demonstrate that EffiTest2 can reduce the number of frequency stepping iterations by more than 94% with only a slight yield loss.