| 摘要 |
PROBLEM TO BE SOLVED: To enable sufficient optical cleaning or a photosensitive surface of an optical element substrate, by causing a cleaning light to be incident from a direction opposite to the proceeding direction of an exposure light. SOLUTION: A projection optical system PL is optically cleaned by a pulse light cast thereon from a backward light emitting system 21. In this case, sine the pulse light proceeds from the side of a water stage WS in a direction opposite to an exposure light, the pulse light is cast on a surface opposite to the surface optically cleaned by the exposure light. Therefore, a contaminant attached on the surface of projection optical system PL on the wafer side which cannot be perfectly removed by the exposure light from the reticle side can be removed. By scanning the wafer stage WS by cleaning light also from the backward light emitting system 21 in parallel with bank pulses before exposure, optical cleaning can be carried out also with the light from the backward light emitting system 21 cast on the surface of the projection optical system PL on the wafer stage side. Therefore, the optical cleaning time can be reduced. |
