Improvement of lithography process by using a FlexRay illuminator for memory applications

Thomas Huang; Chun-Yen Huang; Tsann-Bim Chiou; Michael Hsu; Chiang-Lin Shih; Alek Chen; Ming-Kang Wei

doi:10.1117/12.879567

22 March 2011 Improvement of lithography process by using a FlexRay illuminator for memory applications

Thomas Huang, Chun-Yen Huang, Tsann-Bim Chiou, Michael Hsu, Chiang-Lin Shih, Alek Chen, Ming-Kang Wei

Proceedings Volume 7973, Optical Microlithography XXIV; 79731X (2011) https://doi.org/10.1117/12.879567
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

As is well recognized, source mask optimization (SMO) is a highly effective means of extending the lifetime of a certain photolithography generation without an expensive upgrade to the next generation optical system. More than an academic theory, source optimization first found practical applications in the debut of the pixel-like programmable illuminator in 2009 for producing near freeform illumination. Based on programmed illumination, related studies have demonstrated a nearly identical optical performance to that generated by the conventionally adopted diffractive optical element (DOE) device without the prolonged manufacturing time and relatively high cost of stocking up various DOEs. By using a commercially available pixel-like programmable illuminator from ASML, i.e. the FlexRay, this study investigates the effectiveness of FlexRay in enhancing image contrast and common process window. Before wafer exposure, full SMO and source-only (SO) optimization are implemented by Tachyon SMO software to select the optimum illumination source. Wafer exposure is performed by ASML XT:1950i scanner equipped with a FlexRay illuminator on a critical layer of DRAM process with known hotspots of resist peeling. Pupil information is collected by a sensor embedded in the scanner to confirm the produced source shape against the programmed source and the optically simulated CD. When the FlexRay illuminator is used, experimental results indicate that lithography hotspots are eliminated and depth of focus is improved by as much as 50% in comparison with those from a traditional AERIAL illuminator. Regular focus-exposure matrix (FEM) and the subsequent critical defects scanning reveal that the common process window of the tight-pitched array and the periphery can be enhanced simultaneously with no hotspot identified. Therefore, a programmed source is undoubtedly invaluable in terms of additional manufacturing flexibility and lower cost of ownership when attempting to improve product yield in high volume production.

Citation Download Citation

Thomas Huang, Chun-Yen Huang, Tsann-Bim Chiou, Michael Hsu, Chiang-Lin Shih, Alek Chen, and Ming-Kang Wei "Improvement of lithography process by using a FlexRay illuminator for memory applications", Proc. SPIE 7973, Optical Microlithography XXIV, 79731X (22 March 2011); https://doi.org/10.1117/12.879567

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