Evaluation of exposure dose repeatability in synchrotron radiation lithography

The stabilization of exposure dose repeatability is one of the key factors in reducing the critical dimension variation in synchrotron radiation litho graphy. We have evaluated and improved the exposure dose repeatability of t he full field exposure system, which employs a cylindrically convex mirror. The beam size spreads with the stored current in the storage ring, which c auses the major exposure dose errors. The maximum exposure dose error is ev aluated to be +/-4.0% according to the ray trace simulation, and it is expe cted to reduce the error to +/-0.6% using exposure time compensation. We ha ve evaluated the improvement of the exposure dose repeatability experimenta lly by using the stabilized resist process. Critical dimension variations o f less than +/-2 nm between six wafers exposed over several days were obtai ned. This result indicates that the practical exposure dose error is almost consistent with the calculated value, having a variation of less than +/-1 .0%. (C) 2000 American Vacuum Society. [S0734-211X(00)00602-8].