Patent ID: 7875865
Filing Date: 2011-01-25
Classification: B82Y,G01J,G03F,H05G

Abstract:
1. An illumination system, comprising: an EUV light source; a first arrangement comprising a first aperture stop and a first EUV position sensor, the first arrangement being configured to measure at least one property selected from the group consisting of intensity fluctuations of the EUV light source, position changes of the EUV light source, intensity fluctuations of an intermediate image of the EUV light source, and position changes of the intermediate image of the EUV light source; and a second arrangement comprising a second aperture stop and a second EUV position sensor, wherein the first arrangement is configured so that the aperture stop can allow a solid angle range of radiation originating from the EUV light source to fall on the first EUV position sensor, and/or the first arrangement is configured so that the first aperture stop can allow radiation originating from the intermediate image of the EUV light source to fall on the first EUV position sensor.