Precise optical constants: determination and impact on metrology, simulation, and development of EUV masks

• DOI: 10.1117/12.2643246
• Publication Date: 2022-11-10T22:25:31Z
• Authors: Qais Saadeh; Hazem Mesilhy; Victor Soltwisch; Andreas Erdmann; Richard Ciesielski; Leonhard Lohr; Anna Andrle; Vicky Philipsen; Devesh Thakare; Christian Laubis; Frank Scholze; Michael Kolbe
• Keywords: Extreme Ultraviolet Lithography; Extreme ultraviolet; Photomask; Critical dimension

The interaction of matter and light can be described based on optical constants, shortly called δ&β. These constants provide the fundamental basis for design any system. In Extreme Ultraviolet (EUV) spectral range, however, existing data many materials or compounds is very sparse, non-existent exhibit considerable discrepancies between different sources. This further complicated since scaling effects stipulate response a thin film to differ from bulk. Oxidation, impurities interdiffusion significantly affect system EUV radiation. For this reason, Physikalisch-Technische Bundesanstalt (PTB) establishing new database in cooperation with other European partners. database, designated as Optical Constants Database (OCDB) accessed online freely (OCDB.ptb.de). collection shall support development various fields metrological techniques, like scatterometry computational lithography EUV. demonstrated exemplarily here by interplay δ&β dimensional parameters respect structured TaTeN photomask. It equally important either direction, derive structure measured scattering vice versa predict geometrical structure. addition, impact varying δ β expected imaging performance will investigated simulating typical lithographic image metrics Critical Dimension (CD), best focus position, contrast (NILS) non-telecentricity through pitch L/S 16 nm vertical Lines 32 NA=0.55 scanner mask absorber representatives high-k materialsand an example effect simulation.