Performance analysis of double-fluid-layer achromatic ArF immersion interference lithography

ArF immersion interference lithography system can produce high resolution periodic pattern as a powerful tool for the study of hyper numerical aperture ArF immersion lithography. The coherence requirements on exposure source can be alleviated and high resolution imaging can be realized by the use of achromatic ArF immersion interference lithography system. A novel double-fluid-layer achromatic immersion interference lithography system is developed. The system's achromatic principles and imaging mechanism are studied by using diffraction theory and principle of geometrical optics. The imaging performance is analyzed and the advantages are summarized compared with traditional single-fluid-layer system. The results indicate that this system enables a large depth of focus (DOF) and width of resolved imaging field which are independent of the bandwidth of laser. The system's performance is insensitive to environment, so that the imaging stability is improved. The system employs simple symmetry structure to overcome the problem of poor coherence properties for ArF excimer lasers, and ensures stability of imaging performance in interference lithography.