| abstract |
At least one optical element having a surface, such as a multilayer collection mirror; A laser source for generating a laser beam; And a source material irradiated by a laser beam for forming a plasma and emitting EUV light. In one form, the source material consists essentially of the tin compound and generates tin debris by plasma formation deposited on the optical element, and the tin compound may also contain elements effective for etching the deposited tin from the optical element surface. Can be. Tin compounds may include SnBr 4 , SnBr 2 , and SnH 4 . In another form, the EUV light source may comprise a molten source material irradiated by a laser beam to form a plasma and emit EUV light, the source material being tin and at least one other metal, such as tin, Gallium and / or indium. |