Abstract

Multilayer-coated Schwarzschild imaging objectives have been used to demonstrate high-resolution soft-x-ray imaging.^1-2 In our previous work³ a 20x reduction Schwarzschild imaging objective served a useful tool for studying the mounting and alignment of soft-xray optical elements and the quality and alignment of the condensing optics. However, the field of view, 25 μm by 50 μm, is much too small for a practical lithography tool. We have optimized and fabricated a new Schwarzschild system to achieve a 0.4 mm diameter field of view using 0.1 μm design rules. The increased field of view, although not large enough for a practical lithography tool, approximates the ring width in practical ring-field designs. This objective also covers enough area on the wafer to perform device fabrication experiments. This paper describes the development and characterization of the imaging system and the supporting illumination system.

© 1993 Optical Society of America