PARTICLE CLEANING OF OPTICAL ELEMENTS FOR MICROLITHOGRAPHY

摘要

An optical assembly serves the purpose of being mounted in a projection exposure apparatus (101) for EUV microlithography and comprises at least one vacuum chamber (70, 71, 68a), at least one optical element (6, 7; 65, 66; 63) arranged in the vacuum chamber (70, 71, 68a), the optical element (6, 7; 65, 66; 63) having an optical surface (18) which may be impinged upon by a useful beam bundle (3) of the projection exposure apparatus (101), and a cleaning device (72) for cleaning the optical surface (18). The cleaning device (72) is configured to perform particle cleaning of the optical surface (18) at a gas pressure within the vacuum chamber (70,71, 68a) which is higher than a vacuum pressure (p0) for performing an exposure operation with the projection exposure apparatus (101). The result is an optical assembly capable of providing optical elements having an optical surface which may be impinged upon by a useful beam bundle which can be cleaned reliably from foreign particles.