Patent ID: 7423729

Claim:
A method of monitoring a light integrator of a photolithography system, wherein said photolithography system comprises a light source ( 10 ) for illuminating different fields of a photosensitive layer ( 12 ) and a light integrator ( 18 ) for measuring the actual exposure doses of the illuminated fields, comprising the step of illuminating different fields of said photosensitive layer ( 12 ) in succession, wherein in each illumination step the actual exposure dose is measured by means of said light integrator ( 18 ), the actual exposure time is controlled so that said actual exposure dose to which a field of said photosensitive layer ( 12 ) is exposed corresponds to a desired exposure dose, and said actual exposure time is fed to a monitoring system ( 24 ) for in-line monitoring said light integrator ( 18 ) during illumination of said fields, wherein the monitoring system performs a calculation using the actual exposure time to determine if the light integrator has malfunctioned.