Abstract

A four-bounce two-element projection system designed to achieve 0.14 μm resolution over a 1.2x5 mm² ring field has been fabricated. The radiation transport properties of both the individual multilayer-coated optics and the assembled system has been measured. The individual mirror measurements demonstrated that the coatings were within 0.03 nm of d-spacing specifications; however, the mirrors exhibited significant scatter which reduced reflectance below the design specification of 60%. The peak radiation transport efficiency of the assembled projector was 7% at 13.2 nm. To the best of the authors’ knowledge, this represented the first measurement of the radiation transport efficiency of a multi-element optical system for EUV lithography. Experiments performed at LLNL’s front-end test bed facility were consistent with the measured transport efficiency.

© 1994 Optical Society of America