Long pulse duration of F2 laser for 157-nm lithography

ABSTRACT An ultra narrow line width of the F 2 laser, narrower than 0.2pm, is required for a CaF 2 only refractive optics exposure system. Also, a low peak laser power is needed for the extension of the optics lifetime. These ultra narrow line width and low peak power are achievable by long pulse duration. We, Association of Super-Advanced Electronics Technologies (ASET), are developing an ultra line narrowed F 2 laser below 0.2pm, with 5mJ high output energy, by adopting a 2-stage F 2 laser system, which consists of an oscillator and an amplifier. The oscillator for this 2-stage system is required to have an ultra narrow line width of below 0.2pm. We have developed F 2 laser with very long laser pulse duration of over 65ns (Tis: the integral squire pulse width), in a free running operation. And , by installing a line-narrowing module (LNM) in this F 2 laser, an ultra narrow line width of below 0.2 pm (FWHM, deconvolved) has been realized. This F 2 laser was successfully used for the osc illator of 2-stage system