Method for cleaning reflective optical element for illumination- and projection system, involves removing metallic deposits from optically utilized surface of reflective optical element by performing wet-chemical treatment

摘要

The method involves removing metallic deposits from an optically utilized surface of a reflective optical element by performing wet-chemical treatment. A surface of the reflective optical element is moistened with an aqueous alkaline solution i.e. aqueous sodium hydroxide solution. Temperature of the reflective optical element is monitored during cleaning for controlling whether boiling temperature is exceeded from 60 degree Celsius. A glass surface to be cleaned is electrically grounded during the cleaning.