Abstract
Off-axis illumination is one of the key resolution enhancement technologies in projection lithography systems. Phase type diffractive optical elements are adopted by most of the lithography machine manufacturers to realize off-axis illumination. In this paper, a method of pupil shaping for off-axis illumination in optical lithography is introduced which contains a zoom beam expander, circularly symmetric diffractive optical elements, and a Fourier lens. The method could produce the required illumination pattern for off-axis illumination at the pupil plane. Compared with the conventional method of off-axis illumination, the method in this paper could eliminate deterioration of the pupil thoroughly and reduces the difficulty of the optical design of the zoom lens. Based on this method, several circularly symmetric diffractive optical elements are designed for experiments, and a remarkable improvement in eliminating deterioration of the pupil is observed compared with the conventional method.
© 2016 Optical Society of America
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