The Manufacture of Depolarizer in Transform System of Immersion Photolithography Polarization State

To meet the requirements of 45nm node ultraviolet lithography exposure optical system with 193nm wavelength and 1.35 NA for high resolution in extremely large scale integrated circuit. A depolarizer is designed to implement high quality polarization mode lighting on mask surface.In this paper, the depolarizer in the polarization transformation module is designed and the AR film in the depolarizer is developed, combination of two wedge shaped quartz crystals with a diameter of 50 +/- 0.2mm is used to realize beam depolarization, with optical axes of two crystals are at an angle of 45 degrees in space. The front one achieves depolarization and the back one compensates optical path. The reflectivity of the prepared AR film is less than 99.5% at 193nm, this depolarizer solved a series of problems caused by the sharp reduction of focal depth due to the increase of NA and the shortening of exposure wavelength, therefore, the development of this depolarizer has certain application value.