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Proceedings Paper

Improvement of lithography process by using a FlexRay illuminator for memory applications
Author(s): Thomas Huang; Chun-Yen Huang; Tsann-Bim Chiou; Michael Hsu; Chiang-Lin Shih; Alek Chen; Ming-Kang Wei
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Paper 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.

Paper Details

Date Published: 22 March 2011
PDF: 11 pages
Proc. SPIE 7973, Optical Microlithography XXIV, 79731X (22 March 2011); doi: 10.1117/12.879567
Show Author Affiliations
Thomas Huang, Nanya Technology Corp. (Taiwan)
Chun-Yen Huang, Nanya Technology Corp. (Taiwan)
Tsann-Bim Chiou, ASML Technology Development Ctr. (Taiwan)
Michael Hsu, ASML Strategic Marketing (Taiwan)
Chiang-Lin Shih, Nanya Technology Corp. (Taiwan)
Alek Chen, ASML Technology Development Ctr. (Taiwan)
Ming-Kang Wei, Nanya Technology Corp. (Taiwan)

Published in SPIE Proceedings Vol. 7973:
Optical Microlithography XXIV
Mircea V. Dusa, Editor(s)

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