Study on Aging Effect of Optical Film under High Intensity of UV Exposure

In the semiconductor industry, for lithography system the reflective film coated on the mirror and the antireflective film coated on the correction lens in the projection lens module were usually irradiated by the high intensity of I-line light, and the optical film will gradually age and become matte after using a period of time. In order to investigate the ingredient variation and aging effects of the optical film caused by i-line light, a UV light irradiation environment was built with an optical power of 80 mW. In the experiment, the reflective and anti-reflective film was coated on the BK-7 glass and irradiated by 24 to 120 hours. Then, the reflectivity/transmittance and the ingredient of optical film was measured and analyzed. The reflectivity and transmittance of optical film varied after 24 hour irradiation and decreased approximately 1.67 and 0.9 wt% after 120 hours irradiation, respectively. In addition, the results obtained from the focused ion beam (FIB) system indicated that the ingredient of oxygen of both films increased and the anti-reflective film ruptured evidently under 120 hours of irradiation. The results from the manuscript can serve as reference information for durability evaluation of optical film employed in the projection lens module in the semiconductor