| 摘要 |
An extreme ultraviolet (EUV) light source to detect fluctuations in the angular distribution of its output radiation wherein a solid raw material is irradiated with a laser beam to generate a vapor. The vapor is subjected to an electrical arc generated between a pair of discharge electrodes to generate a high temperature plasma that emits EUV radiation. The EUV radiation is collected along an optical axis toward a focal point by a plurality of concentrically arranged reflectors. A plurality of EUV radiation detectors are arranged around a circular ring centering on the optical axis of the concentrically arranged reflectors. Each EUV radiation detector includes two spaced apart diaphragms with a pinhole. The pinholes are aligned with a virtual line connecting with the focal point. EUV radiation passing through the pinholes strikes a light detecting element in the detectors. The angular distribution fluctuation of the EUV radiation collected at the focal point is obtained based upon irradiance data provided by the light detectors. |
