<title>Compact ArF excimer lasers specific to microlithography and surgery</title>

Abstract

ABSTRACT High repetition rate operation technology and spectral narrowing technology with compact excimer lasers whosecross-sectional dimensions are around 120 x 120 mm. High repetition rate operation over 1 .5 kHz and spectral narrowing to 1pm are reported.These technologies are essential to promising applications of ArF excimer lasers. High resolution pattem of 0.16 imline and space is demonstrated by an optical laser lithography with the compact ArF excimer laser. The smallest AsP excimerlaser specific to the photo-chemical surgery of cornea is also presented.Keywords: excimer laser, ArF, high repetition, spectral narrowing, lithography, projection optics, DRAM, PRK, cornea 1. INTRODUCTION Excimer laser market has been growing up remarkably due to the maturity of excimer laser technologies and to alarge growth in its applications, in recent years. Most of excimer lasers which are applied to excimer laser-stepper for 64Mbit and 256 Mbit dynamic random access memory (DRAM), laser drilling of print-heads for ink-jet printers, photo chemi-cal surgery for cornea and so on. However, technologies such as the high repetition rate oscillation and spectral narrowingare immature for ArF excimer laser, and essential to promising applications of next generations.The innovation in the field of a LD pumped solid state laser and harmonic generation with a nonlinear crystal is alsoremarkable. Ultraviolet(UV) light source are obtained with harmonics generation of the infrared-red LD pumped solid statelaser with high efficiency of several tens percent. Part of KrF and XeCl excimer lasers will be replaced by solid state lasersafter their improvements in the average power in the near future. Replacement of ArF excimer lasers by solid state lasers isdifficult ,because vacuum ultra-violet (VUV) radiation with solid state lasers is problematic. Low conversion efficiency andlow damage threshold of a nonlinear crystal have not been improved yet in the wavelength range shorter than 200 am.Our researches have been focused on ArF excimer laser by reasons described above. Advanced technologies aredescribed in section 2. Compact ArF excimer lasers specific to hot applications such as an optical lithography and a photo-chemical surgery are described in section 3.