Design dependent process monitoring for back-end manufacturing cost reduction
Tuck-Boon Chan, Aashish Pant, Lerong Cheng, Puneet Gupta · 2010
AbstractShort-loop process monitoring structures (usually simple device I V, C V measurements made after M1 fabrication) are commonly put in wafer scribe-lines. These test structures are almost always design independent and measured/monitored by the foundry to keep track of process deviations. We propose a design-dependent process monitoring strategy which can accurately predict design performance based on simple Ieff-based delay and Ioff-based leakage power estimates. We show that our strategy works much better (0.99 correlation vs. 0.87) compared to conventional design-independent monitors. Further, we use the predicted delay and leakage power for early yield estimation for pruning bad wafers to save test and back-end manufacturing costs We show that wafer pruning based on our approach can achieve upto 98 % of the maximum achievable benet/prot. We design the measurement and prediction schemes so as to minimize data as well as computation that needs to be kept track of during wafer fabrication. Such design-dependent process monitoring can help target process control/optimization effort, enable quicker yield ramp besides saving test and manufacturing costs. I.