FOCUSING OPTICAL SYSTEM, LIGHT SOURCE UNIT, ILLUMINATION OPTICAL APPARATUS, AND EXPOSURE APPARATUS

摘要

A light source unit of EUV light is disclosed which comprises a plasma light source emitting EUV lights, a collector mirror having a spheroidal reflecting surface, and an auxiliary collector mirror having a spherical reflecting surface. The collector mirror is arranged so that the plasma light source is on the first focal point of the collector mirror, while the auxiliary collector mirror is arranged so that the plasma light source is not on the spherical center of the auxiliary collector mirror.