ILLUMINATION SYSTEM WITH VACUUM CHAMBER WALL HAVING TRANSPARENT STRUCTURE

摘要

A lithographic projection apparatus has a discharge plasma radiation source (LA) that is contained in a vacuum chamber (10). The radiation source is to generate a beam (PB) of EUV radiation. A chamber wall of the vacuum chamber incorporates a channel structure comprising adjacent narrow channels (11) that are substantially parallel to a propagation direction of the radiation beam and have a width that decreases or increases along the beam axis in accordance with the beam vergence. This structure passes the beam to another subsequent vacuum chamber (20) maintained at a much higher vacuum level (lower pressure).