Lens-cementing technology used in optical system of DUV wavelength region -Selection of optical cement and degradation evaluation by DUV irradiation-

摘要

In this paper, a newly developed optical lens cementing technology is reported. Here, a fluoride material is used as an optical cement which can reduce damage from DUV radiation. The degradation of transmittance and the accuracy of surface of the cemented optical elements including adhesive used for cementing have been evaluated after prolonged DUV irradiation. It has been shown that with 248 nm wavelength this cement works quite well, and moreover, even with 193 nm wavelength, when used for 1000 hours, the change in transmittance was negligible where average irradiation power was kept within 300mW/cm~2. Hence for all practical purpose the use of this cement in microscope objective is quite acceptable for 248 nm applications, thus confirming that this cementing technology is satisfactory and meets the performance requirement of DUV inspection systems.