Effect of Electron Beam Orbit Distortion on Optical Performance of the Synchrotron Radiation Lithography Beamline.

We have investigated the effect of the synchrotron radiation (SR) source drifts, namely, the source position and emission angle, caused by electron beam closed orbit distortion (COD) on optical performance of the beamline such as the exposure field size, the illumination intensity and the uniformity. We theoretically derived that SR source drifts should be controlled within ± 0.4 mm and ± 0.2 mrad for the position and emission angle drifts, respectively, to obtain uniformity better than 15% for our beamline. We also propose a new technique to directly measure the SR source drifts using the focusing property of the mirror and the SR beam monitor installed in the beamline, which can be applied to predict the changes of optical performance of the beamline, and to monitor the electron beam drifts for correcting COD.