A stage for processing a substrate, especially useful for vacuum applications, has a recess just large enough to hold a substantially flat substrate and a chuck or holder but not much more. The perimeter of the recessed side has an air bearing surface separated from the recess by differentially pumped groves and seal lands. The air bearing lands are urged against a reference plate guide surface and the seal lands being substantially coplanar create a resistance to flow between the groves and recess, on the other side of the base reference plate mounts the radiation source. The VCS may operate in a vacuum environment itself, or in another preferred embodiment, it provides the possibility for multiple stages moving between process or inspection steps within the same tool or process sequence.