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.
To maintain lithographic pitch scaling, extreme ultraviolet (EUV) processes have been adopted in high-volume manufacturing (HVM) for today’s advanced logic and memory devices. Among various defect sources, stochastic patterning defects are one of the most important yield detractors for EUV processes. In this work, we will limit our scope to patterning defects arising out of lithography. In the past, it has been shown that the patterning defect process window is often limited by stochastic hotspots. These hotspots have very low failure probabilities in a well-optimized process, and hence their detection necessitates large area sensitive defect inspection, such as with a broadband plasma (BBP) optical defect inspection system. It has also been shown that systematic issues in design can be exacerbated by stochastic variations. Hence, it is critical to discover these hotspots and study their variability with massive SEM metrology. Such analyses can uncover systematic trends, which can then be corrected and monitored. In this work, we discover hotspots using broadband plasma (BBP) optical inspection and study their variability using KLA’s aiSIGHT™ pattern-centric defect and metrology software solution for automatic defect classification and SEM metrology measurements. We also demonstrate the need for fast and rigorous 3D probabilistic stochastic defect detection on design as a continuation of this work.
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.
Mask-shops developing advanced reticles for use in high-volume semiconductor manufacturing generate an abundance of critical data. Most of this data is generated in the backend of the mask production line where critical dimensions (CDs), registration and defect inspections are performed, and the general emphasis of this data collection is to confirm that the mask meets certain required specifications. Some of the results gathered are also used to monitor the front-end of line processing steps like mask write, develop, etch and clean. However, with most data being disparate and staying local to the tools where they were gathered, very little gets used beyond the immediate need to disposition the mask for shipment. This extensive data, when effectively stored and analyzed, helps not only accelerate time-to-results for mask disposition but also substantially improve monitoring of the frontend process and root-cause analyses. This paper discusses requirements for an effective data management system (DMS) capable of centralizing all maskshop data. This involves not only centralizing blank and pattern defect inspection results and the associated review SEM, repair, and AIMSTM disposition data but also CD, registration and other metrology data collected. The DMS architecture needs to support connectivity and use of data from other databases in the maskshop which include production tracking, computational application results, tool and fab environment logs, etc. After centralizing the data and establishing linkage to other databases, the system needs to provide visualizations through user-interfaces and advanced analytics that are easy for use by both production and engineering. The paper introduces the new KlearViewTM mask DMS system from KLA and discusses it’s features and deployment into advanced mask manufacturing. While quintessential to maskshop operations, the DMS also serves as a bridge to reticle requalification and wafer inspection and metrology data critical to improving mask quality and qualification necessary for achieving optimal EUV lithography cost-of-ownership.
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