Immersion Lithography: Photomask and Wafer-Level Materials

Optical immersion lithography utilizes liquids with refractive indices >1 (the index of air) below the last lens element to enhance numerical aperture and resolution, enabling sub-40-nm feature patterning. This shift from conventional dry optical lithography introduces numerous challenges requiri...

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Bibliographic Details
Published in:Annual review of materials research 2009-08, Vol.39 (1), p.93-126
Main Authors: French, Roger H., Tran, Hoang V.
Format: Article
Language:English
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Summary:Optical immersion lithography utilizes liquids with refractive indices >1 (the index of air) below the last lens element to enhance numerical aperture and resolution, enabling sub-40-nm feature patterning. This shift from conventional dry optical lithography introduces numerous challenges requiring innovations in materials at all imaging stack levels. In this article, we highlight the recent materials advances in photomasks, immersion fluids, topcoats, and photoresists. Some of the challenges encountered include the fluids' and photomask materials' UV durability, the high-index liquids' compatibility with topcoats and photoresists, and overall immersion imaging and defectivity performance. In addition, we include a section on novel materials and methods for double-patterning lithography—a technique that may further extend immersion technology by effectively doubling a less dense pattern's line density.
ISSN:1531-7331
1545-4118
DOI:10.1146/annurev-matsci-082908-145350