Patent ID: 6801562
Filing Date: 2004-10-05
Classification: C30B,H01S

Abstract:
A &gE;4 kHz repetition rate fluoride excimer laser system for producing an UV output of wavelength &lgr;<200 nm, said laser system comprising:an excimer laser chamber for producing an UV wavelength &lgr;<200 nm discharge at a pulse repetition rate &gE;4 kHz, and said chamber having at least one window made from a magnesium fluoride single crystal, for outputting said &lgr;<200 nm discharge as a &gE;4 kHz repetition rate excimer laser &lgr;<200 nm output; wherein said magnesium fluoride window, when exposed to 5 million pulses of 193 nm light at a fluence &gE;40 mJ/cm2/pulse, has an induced absorption of less than 0.08 Abs per 42 mm path length when measured at 255 nm, a 120 nm transmission of at least 30% through said 42 mm path length, and a 200 to 210 nm range absorption coefficient 0.0017 cmâˆ’1.