Magnetic levitation systems compared to conventional bearing systems

So far, guide ways for positioning systems (stages) in semiconductor applications are often equipped with air bearings and/or roller bearings. Although these passive bearing systems are seemingly rather cost-effective, motion performance and motion capabilities are limited compared to active systems using multiple servo loops. So far, nm-level motion performance in 6 degrees of freedom (DoF) was realized through the application of an isolated machine architecture in combination with a hybrid stage concept, i.e., by stacking an active short stroke system providing fine adjustments on top of a passive long stroke system. This paper describes the development of a full 6-DoF active positioning system with nm-level motion performance in one single (long stroke) stage, using active magnetic bearing systems. It is shown that active bearings provide interesting advantages and additional features for substrate positioning, enabling a rather simple and cost effective stage design, suitable for next generation semiconductor applications.