8 November 2012 Mask characterization for CDU budget breakdown in advanced EUV lithography
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Abstract
As the ITRS Critical Dimension Uniformity (CDU) specification shrinks, semiconductor companies need to maintain a high yield of good wafers per day and a high performance (and hence market value) of finished products. This cannot be achieved without continuous analysis and improvement of on-product CDU as one of the main drivers for process control and optimization with better understanding of main contributors from the litho cluster: mask, process, metrology and scanner. In this paper we will demonstrate a study of mask CDU characterization and its impact on CDU Budget Breakdown (CDU BB) performed for an advanced EUV lithography with 1D and 2D feature cases. We will show that this CDU contributor is one of the main differentiators between well-known ArFi and new EUV CDU budgeting principles. We found that reticle contribution to intrafield CDU should be characterized in a specific way: mask absorber thickness fingerprints play a role comparable with reticle CDU in the total reticle part of the CDU budget. Wafer CD fingerprints, introduced by this contributor, may or may not compensate variations of mask CD’s and hence influence on total mask impact on intrafield CDU at the wafer level. This will be shown on 1D and 2D feature examples in this paper. Also mask stack reflectivity variations should be taken into account: these fingerprints have visible impact on intrafield CDs at the wafer level and should be considered as another contributor to the reticle part of EUV CDU budget. We observed also MEEF-through-field fingerprints in the studied EUV cases. Variations of MEEF may also play a role for the total intrafield CDU and may be taken into account for EUV Lithography. We characterized MEEF-through-field for the reviewed features, the results to be discussed in our paper, but further analysis of this phenomenon is required. This comprehensive approach to characterization of the mask part of EUV CDU characterization delivers an accurate and integral CDU Budget Breakdown per product/process and Litho tool. The better understanding of the entire CDU budget for advanced EUVL nodes achieved by Samsung and ASML helps to extend the limits of Moore's Law and to deliver successful implementation of smaller, faster and smarter chips in semiconductor industry.
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Peter Nikolsky, Peter Nikolsky, Chris Strolenberg, Chris Strolenberg, Rasmus Nielsen, Rasmus Nielsen, Tjitte Nooitgedacht, Tjitte Nooitgedacht, Natalia Davydova, Natalia Davydova, Greg Yang, Greg Yang, Shawn Lee, Shawn Lee, Chang-Min Park, Chang-Min Park, Insung Kim, Insung Kim, Jeong-Ho Yeo, Jeong-Ho Yeo, } "Mask characterization for CDU budget breakdown in advanced EUV lithography", Proc. SPIE 8522, Photomask Technology 2012, 85220P (8 November 2012); doi: 10.1117/12.970395; https://doi.org/10.1117/12.970395
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