A line-narrowed ArF excimer laser are being developed as a light source for 193 nm lighography using a refractive lens system. The system is required a narrow spectral bandwidth, high laser output stability and long lifetime. In this laser, we present a newly developed sub-picometer ArF excimer laser for lithography.
The prototype laser, as shown in this paper, utilizes an all solid state pulse power modulator with 2-stage magnetic pulse compressors. A barrier discharge excimer lamp technology 1) developed by USHIO is adopted as a pre-ionization method. The materials that constitute this laser are carefully selected to prevent the impurity generation. A long gas life time of over 4×107 shots has been confirmed in a broad-band operation.
The line-narrowing optics in this laser consists of a combination of prism beam expanders and a grating. Figure 1 shows a spectral profile measured by an etalon system with a FSR of 6 pm and a reflection finesse of about 30. Figure 2 shows an ingegrated energy distribution. More than 5 mJ of pulses with of below 0.6 pm FWHM and 95％ of the spectral energy lying within a 2 pm were obtained. The laser output stability and the spectral stability will be also presented.