Mask defectivity remains a key focus area for the enablement of extreme ultraviolet (EUV) lithography in high-volume manufacturing (HVM) at both mask and IC manufacturing facilities. To improve defect detection on EUV patterns, both mask and wafer inspection tools are operated with high sensitivity and advanced algorithms, coupled with mask SEM and wafer e-beam review tools, all of which generate substantial amounts of data. This data must be thoroughly examined to identify any possible defect source information and improve the overall performance of mask outgoing, fab incoming, and requalification inspections. In this paper, the complete integration of a centralized reticle and wafer data management solution is presented, providing real-time analytics to help identify defect sources, monitor changes in defectivity due to exposure and reticle handling, and recognize systematic patterns of defectivity resulting from reticles used in an HVM flow. By combining reticle data from both the mask shop and requalification line with inline wafer inspection data, including wafer print checks, operators can make correct and timely go/no-go decisions for EUV reticles, minimizing any wafer impact, while engineering teams can obtain detailed information across reticle and wafer lots for defect reduction efforts. By integrating the mask-centric KlearView™ Fab with the wafer-centric Klarity® defect software systems, this comprehensive data management solution improves time to results, enhances the capability to trace defectivity to its source, and improves data continuity between mask and reticle manufacturing sites, thereby enabling EUV manufacturability and production yield.
Mask defectivity continues to be a critical challenge to full industrialization of extreme ultraviolet (EUV) lithography. The most concerning defects are those that originate from the blank substrate or multilayer deposition process and are not easily repaired or compensated for. These can best be avoided by hiding them underneath the unexposed absorber regions of the reticle layout. In this paper, we present a comprehensive blank defect avoidance solution that substantially mitigates the risk of printing blank defects. In the first step of this solution, we apply an automatic defect classification to all available blank inspections, categorizing defects into various critical and noncritical bins. In the second step, we register these defects to very high accuracy using a mask registration tool. In the final step, we use a fast polygon-based nonlinear optimization algorithm that outputs the best possible placement of all critical defects so that they are located under the absorber patterns. It does so by optimizing the global mask pattern shift and rotation and accounts for uncertainty in defect positioning and E-beam writing. After the optimal reticle shift and rotation are computed, they are verified by simulating possible wafer print impact. An overall impact score is computed for that specific combination of blank and pattern file and done so for all available blanks in the unused blank database. The E-beam writer operator can then select the blank with the lowest impact score or least risk of printing. Integrated within the KLA RDC and KlearView™ systems, this comprehensive extreme ultraviolet (EUV) blank defect avoidance solution has been validated in pilot production. By maximizing entitlement of EUV blanks across various grade levels, this solution has helped reduce costs and improve yields.
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