Patent ID: 9127981
Filing Date: 2015-09-08
Classification: G01J,G03F,H01L,H05G

Abstract:
1. A return beam diagnostics system for measuring light reflected from a target in a laser produced plasma extreme ultraviolet light source, comprising: an optical switch located on an optical input path that receives the light reflected from the target when the target is illuminated by a laser source, a light blocking element located on the first optical output path; a sensing device located on the second optical output path, the sensing device configured to measure the received reflected light; and a controller configured to respond to a first laser source firing signal by directing the optical switch to perform a measurement sequence of: the controller further configured to respond to a second laser source firing signal by repeating the measurement sequence if the second laser source firing signal is received at the controller after the first predetermined period of time plus a second predetermined period of time, else ignoring the second laser source firing signal received at the controller.