Development status of projection optics and illumination optics for EUV1

Abstract

Final adjustment of EUV1 projection optics was completed and its performance was evaluated. Wavefront error of 0.6nmRMS in average through the exposure field was achieved. The maximum and minimum wavefront errors in the whole field were 0.8nmRMS and 0.3nmRMS, respectively. Flare of the projection optics was estimated from the measured power spectrum density (PSD) of each aspheric mirror of the projection optics. The flare value for Kirk pattern with the radius of 1μm was estimated to be about 10%. Completed projection optics was installed into the main body of EUV1. Optimization of polishing process was further pursued. Consequently, LSFR of 38pmRMS, MSFR of 80pmRMS and HSFR of 68pmRMS were achieved. Assemble of the illumination-optics unit for EUV1 was completed and its performance was evaluated using an illumination-optics test stand. Irradiation uniformity on the mask plane, pupil fill and so on were measured with the test stand using a visible light and EUV radiation. Completed illumination-optics unit was installed into the main body of EUV1. Reflection-type spectral purity filter (SPF) and high-NA projection-optics design were investigated as new R&D items for the future optics of EUV exposure tools.