Performance analysis of ArF excimer laser lithography optics

In ArF excimer laser lithography, catadioptric systems are widely used as projection optics. These systems consist of a mirror, a polarizing beam splitter, quarter wave plates and corrector lenses. Combination of a polarizing beam splitter and a quarter wave plate is used to separate the forward and backward beam and to remove the central obscuration. The life time of the ArF excimer laser optics is limited by the well-known defect, the compaction of fused silica. The compaction is proportional to the square of energy density, and the life time is given by the inverse of compaction. If we make the image space working distance longer, the energy density becomes smaller and the life time becomes longer. We have designed two examples of catadioptric systems and analyzed their optical performances and life times. Also we have reviewed the relationships between the working distance and the size of optical component, however, there is a strong relationship between both of them. The longer working distance makes the optical component larger. It has the significant meaning in optics design, because the big sized optical material, which can be used at 193 nm, is very rare. Especially, the material for prism of polarizing beam splitter is hard to attain. Hence there should be some compromises between the working distance and the size of optical components.