Improved x-ray mirrors for synchrotron radiation (SR) lithography have been developed and installed in our beamlines. The optimum grazing angle of a platinum (Pt) coated mirror which effectively converges SR beams is derived. The surface roughness of the Pt films is measured by using an optical surface profiler, an STM, and x-ray reflectivity measurements. It is found that x-ray reflectivity strongly depends on the surface micro structure. Improved vacuum evaporation and ECR sputtering are used to coat Pt film on the mirror surfaces. Using the improved vacuum evaporation film, the surface roughness is 1 nm and reflectivity is 50% at a 1.8 degree grazing angle, at a 8.34 A wavelength. Using the ECR sputtering film, surface roughness is below 0.3 nm and reflectivity is above 60%. A two-toroidal mirror device is used to increase the x-ray intensity on the wafer and to vertically expand the exposure area. Astigmatism is intentionally introduced in these mirrors to increase their converging and collimating abilities. A divergence angle of 2 degrees and an exposure area of 25 X 25 mm² are obtained by using Pt-coated astigmatic toroidal mirrors. The resulting x-ray intensity on the wafer is 0.05 mW/cm²/mA and the peak wavelength is about 7 to 8 A.

Date Published: 20 October 1992
PDF: 8 pages
Proc. SPIE 1720, Intl Symp on Optical Fabrication, Testing, and Surface Evaluation, (20 October 1992);

Published in SPIE Proceedings Vol. 1720:
Intl Symp on Optical Fabrication, Testing, and Surface Evaluation
Jumpei Tsujiuchi, Editor(s)