High efficiency beamline for synchrotron radiation lithography

Abstract
A highly efficient beamline for synchrotron radiation (SR) lithography has been developed for our compact storage ring (Super‐ALIS). Two toroidal mirrors are employed 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. The first mirror converges SR beams with a divergence angle of 2°. The second mirror, which is controlled by a microcomputer, collimates the beam and oscillates to produce an exposure area of 25×25 mm2. An improved vacuum evaporation technique is used to coat the mirror surfaces with platinum, which increases the reflectivity to 50% at a wavelength of 8.34 Å. The resulting x‐ray intensity on the wafer is 5 mW/cm2/100 mA. A uniform x‐ray intensity distribution can be obtained by adjusting the scan speed of the second mirror and using an x‐ray compensation filter. The resulting nonuniformity is improved to be less than ±4%. A reliable x‐ray extraction system that consists of two Be windows and a SiN window permits exposure in an atmospheric environment.

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