Patent ID: 6456361
Filing Date: 2002-09-24
Classification: G03F

Abstract:
A method of measuring a vacuum ultraviolet light beam having a wavelength not longer than 190 nm, said method comprising:a first step of passing a regular light beam having a wavelength longer than 190 nm through an optical unit; a second step of adjusting a position of an achromatic lens system included in said optical unit such that the regular light beam which passed through said optical unit is focused on a light detector, said achromatic lens system being composed by combining one single lens produced from fluorite with another single lens produced from fluorine-doped synthetic quartz so as to fulfill achromatic conditions for both the regular light beam and the vacuum ultraviolet light beam; a third step of conducting, after the second step, one of (i) evacuating the inside of a housing for enclosing said optical unit and said light detector and (ii) purging the inside of said housing by using nitrogen gas; and a fourth step of focusing, after the third step, the vacuum ultraviolet light beam which passed through said optical unit on said light detector so as to measure the vacuum ultraviolet light beam.