Investigation of cross-field wavefront aberrations of KrF lithography exposure systems as a function of excimer laser bandwidth

Ivan Lalovic; Armen Kroyan; Nigel R. Farrar; Dennis Taitano; Paolo Zambon; Adlai H. Smith

doi:10.1117/12.435655

14 September 2001 Investigation of cross-field wavefront aberrations of KrF lithography exposure systems as a function of excimer laser bandwidth

Ivan Lalovic, Armen Kroyan, Nigel R. Farrar, Dennis Taitano, Paolo Zambon, Adlai H. Smith

Author Affiliations +

Proceedings Volume 4346, Optical Microlithography XIV; (2001) https://doi.org/10.1117/12.435655
Event: 26th Annual International Symposium on Microlithography, 2001, Santa Clara, CA, United States

Abstract

Quantification of projection lens aberrations in lithographic exposure systems has gained significant importance due to more stringent critical dimension control and image fidelity requirements. As linewidths shrink, the impacts of wavefront aberrations on imaging become more pronounced. Therefore, minimization of the wavefront aberrations across the image field is desired and has led to the development of a number of measurement approaches. The proposed techniques have been evaluated extensively for characterization and specification of lens systems, adjustments, matching, and periodic control and monitoring of lithography systems for volume production. In this study, we discuss the contribution of excimer laser bandwidth towards lens aberrations. We carry out simulations of the effects of image contrast on conventional projection patterning, to evaluate the degree of aberation-induced linewidth changes depending on image contrast level. Also, experiments have been conducted to measure the response of wavefront error as a function of spectral bandwidth for a 0.6NA stepper and scanner. Depending on the field location, a positive relationship is observed between the measured aberration level and bandwidth. We propose a formalism to correlate the aberration measurement with aberration response to wavelength offset, presented elsewhere.[2] The wavefront error, in this work, is measured using a commercially available in-situ interferometric technique, whose response is largely insensitive to focal plane changes and partial coherence.

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Ivan Lalovic, Armen Kroyan, Nigel R. Farrar, Dennis Taitano, Paolo Zambon, and Adlai H. Smith "Investigation of cross-field wavefront aberrations of KrF lithography exposure systems as a function of excimer laser bandwidth", Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); https://doi.org/10.1117/12.435655

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