Diffractive lateral-shearing interferometer for phase-shift mask measurement using an excimer laser source

Johannes Schwider; Gerald Fuetterer; Norbert Lindlein

doi:10.1117/12.611690

14 February 2005 Diffractive lateral-shearing interferometer for phase-shift mask measurement using an excimer laser source

Johannes Schwider, Gerald Fuetterer, Norbert Lindlein

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Proceedings Volume 5776, Eighth International Symposium on Laser Metrology; (2005) https://doi.org/10.1117/12.611690
Event: Eighth International Conference on Laser Metrology, 2005, Merida, Mexico

Abstract

The physical limits of optical lithography are mainly determined by the aperture of the mask projection system and the wavelength of the light. In addition to the wavelength shift to the deep UV the application of special techniques to improve the processing window are required. This has furthered the application of the phase shift mask as a lithography tool. The generation of the exact intensity distribution needed in the plane of the wafer strongly depends on the accuracy of the phase shift introduced by the phase shift mask. However, one difficult issue is the reliable measurement of the phase shift introduced by the phase mask at the working wavelength. This is of course mainly due to the lack of suitable and simple interferometric devices for the deep-UV-region -- here 193 nm. We propose the use of a diffractive shearing interferometer as a way out. By combining two Ronchi-phase gratings in series it is possible to produce shear and phase shifts for the evaluation of the fringe patterns simply by axial and lateral shifts of the phase gratings relative to each other. Since the excimer laser emits spatially partial coherent light only, the coherence issue is one of the physical problems dealt with. The state of the art of our experiments will be presented.

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Johannes Schwider, Gerald Fuetterer, and Norbert Lindlein "Diffractive lateral-shearing interferometer for phase-shift mask measurement using an excimer laser source", Proc. SPIE 5776, Eighth International Symposium on Laser Metrology, (14 February 2005); https://doi.org/10.1117/12.611690

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