| 摘要 |
A lithographic projection apparatus includes an illumination system configured to provide a beam of radiation; a support configured to support a patterning device, the patterning device configured to impart the beam of radiation with a pattern in its cross section; a substrate table configured to hold a substrate, and a projection system configured to project the patterned radiation onto a target portion of the substrate. The illumination system includes a plurality of radiation sources; a pupil facet mirror; and a plurality of field facet mirrors, each field facet mirror being associated with one of the radiation sources and each field facet of a given field facet mirror being configured to image the associated source onto one of a plurality of pupil facets on the pupil facet mirror, each pupil facet being adapted to direct the source image received to a predetermined area to form the beam of radiation. To improve image quality, the path length between each field facet and its associated pupil facet is substantially the same for each field/pupil facet pair and the pupil facets have a plurality of different sizes, the size of each depending on a characteristic of the source by which it is illuminated. The radiation sources may emit radiation in the EUV wavelength range.
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