A plausible approach for actinic patterned mask inspection using coherent interferometric imaging

Steven M. Ebstein

doi:10.1117/12.2551621

23 March 2020 A plausible approach for actinic patterned mask inspection using coherent interferometric imaging

Steven M. Ebstein

Proceedings Volume 11323, Extreme Ultraviolet (EUV) Lithography XI; 1132325 (2020) https://doi.org/10.1117/12.2551621
Event: SPIE Advanced Lithography, 2020, San Jose, California, United States

Abstract

Actinic patterned mask inspection (APMI) is the last major part of the infrastructure required for EUV lithography to be developed. A coherent imaging approach is proposed as a plausible solution requiring incremental improvements to available components. Diffractive optics direct a mW 13.5nm coherent beam to the mask and to interfere at the imaging detector. A motion system translates the mask between exposures. A non-iterative algorithm generates a complex reflectivity (mask image) estimate from each interferogram, in real time with GPU hardware. Realistic simulation results and requirements for the system components are presented. Except for the FEL that is likely required, many elements of the system are simpler and likely less costly than an incoherent imager. The system can be configured to image the mask through a pellicle. Of note, focus tolerance is loose as the focal distance is a software parameter.

Citation Download Citation

Steven M. Ebstein "A plausible approach for actinic patterned mask inspection using coherent interferometric imaging", Proc. SPIE 11323, Extreme Ultraviolet (EUV) Lithography XI, 1132325 (23 March 2020); https://doi.org/10.1117/12.2551621

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