Patent ID: 7915600

Claim:
An extreme ultra violet light source apparatus which generates extreme ultra violet light by applying a laser beam to a target, said apparatus comprising: a chamber in which extreme ultra violet light is generated; a target supply unit which supplies one of tin and lithium as a target to a predetermined position within said chamber; a CO 2 laser which applies a laser beam based on pulse operation to the target supplied by said target supply unit so as to generate plasma; a collector mirror which has a multilayer film on a reflecting surface thereof and collects the extreme ultra violet light radiated from the plasma to output the extreme ultra violet light; a first detector which detects an amount of neutral particles emitted from the plasma; a second detector which detects an amount of ions emitted from the plasma; and a control unit which obtains an amount of neutral particles deposited on said reflecting surface of said collector mirror based on a detection result of said first detector and an amount of said multilayer film worn away from said reflecting surface of said collector mirror based on a detection result of said second detector, and thereby adjusts a pulse width and/or energy of the laser beam radiated from said CO 2 laser such that the amount of the neutral particles deposited on said reflecting surface of said collector mirror is not larger than the amount of said multilayer film worn away from said reflecting surface of said collector mirror.