| 摘要 |
An EUV illumination system, for example, for use in a photolithographic apparatus is configured to condition a radiation beam. A hydrogen radical source configured to supply gas containing hydrogen or hydrogen radicals into the illumination system. The hydrogen gas is effective to remove carbonaceous contamination from the surface of a mirror in the illumination system or to form a buffer against unwanted gases. In order to prevent damage by hydrogen that penetrates the mirror, the mirror comprises a layer made of metal non-metal compound adjacent a reflection surface of the mirror. A transition metal carbide, nitride, boride or silicide compound or mixture thereof may be used for example.
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