In an advanced IC fab, reticle inspection issues are critical as even one killer defect on the reticle can potentially affect thousands of wafers. Human errors such as defect mis-classification may lead to 70% of reticle issues that may affect production efficiency or even impact yield. With the adoption of RET techniques like aggressive OPC and SRAF combined with increasing MEEF and smaller defects, reticle dispositioning is becoming even harder and very time consuming in production. Even an experienced engineer may make a mistake especially when dealing with 40nm and below design nodes. The concept of automation to prevent mistakes in operation has been promoted for many years but a comprehensive solution which covers intelligent task assignment and auto reticle dispositioning in volume production has been missing. Working together with KLA, USCXM proposed a detailed methodology to overcome the above difficulties. From the very beginning, USCXM used Systematic Auto Recipe Creation (SARC) to create recipes for reticle inspections even before the reticles arrived in the fab. Also, an “OHT taxi mode” to improve pod utilization combined with the Reticle Management System (RMS) decision tree algorithm intelligently determined reticle inspection frequency based on wafer requirement and tool redundancy. Finally, USCXM automated final reticle dispositioning steps, such as, auto-releasing or auto-holding the reticle based on KLA’s Reticle Analyzer (RA) results. The overall implementation resulted in 25% improvement in inspection capacity and 50% reduction in operational cost compared to the traditional flow. Further, 92% accuracy for reticle auto-dispositioning was achieved with zero under-estimation. This integrated flow has proven to be invaluable for USCXM and is now deployed in full volume reticle manufacturing production.
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