MULTI-BEAM LITHOGRAPHY APPARATUS PROVIDED WITH A DIFFERENTIAL VACUUM SYSTEM

摘要

In an electron-optical lithographic apparatus, objects (34-i) such as semiconductor wafers are fed through the object room (42) in which a comparatively poor vacuum prevails. The electron sources (4-i) of the apparatus must be accommodated in a source space (48) in which a much better vacuum prevails. To this end, the spaces (42, 48) are separated by pressure limiting apertures (PLA) (12-i). In accordance with the invention, the diaphragm that defines the angle of aperture of the beam also functions as the PLA. In this way only one diaphragm is needed instead of two, resulting in a simple construction of the (miniaturized) electron optical columns of the apparatus.