A Vertical X-ray Stepper for SOR Lithography

A vertical stepper for SOR lithography was developed that features a friction-free xy-stage, an optical heterodyne detection system, a rear-feed wafer loader and a real-time digital positioning control. It provides overlay repeatability of better than 25 nm (3 ) and overlay accuracy of 40 nm (3 ). Application of the stepper to the development of the 0.2 μm LSI devices was confirmed.