Furnace purification and metal fluoride crystals grown in a purified furnace

摘要

The invention is directed to a method for growing metal fluoride crystals suitable for use in below 200 nm optical lithography systems, the method comprising including at least the step of heating a crystal growth furnace to a temperature in the range of 1400-2000° C. to purify the furnace by removal of sulfur and chlorine prior to using the furnace for growing metal fluoride single crystals.