METHOD OF FORMING METAL FLUORIDE THIN FILM, FILM FORMING DEVICE, OPTICAL MEMBER AND PROJECTION EXPOSURE SYSTEM

摘要

PROBLEM TO BE SOLVED: To solve the problem in which a crystal of pure metal fluoride is excellent in transmission of an F2 excimer laser beam, but a thin film formed by a general thin film forming method such as vacuum deposition or sputtering, its transmittance decreases greatly and a light transmission reduction in an optical thin film causes a reduction in the transmittance in an optical member such as a lens or a prism. SOLUTION: This thin film forming method comprises a first process in which a metal thin film is formed on a substrate and a second process in which the metal thin film is heated in an atmosphere of fluorine gas to induce a fluorinating reaction.