Excimer laser-based lithography for 0.5 µm device technology

A deep ultraviolet step and repeat system, operating at 248.4 nm, has been developed by retrofitting a commercial system with a KrF excimer laser and custom designed fused silica condenser and projection optics. The 5X projection lens has a minimum field size of 14.5 mm and a variable numerical aperture of 0.20 to 0.38. Resolution of 0.5 µm features over the full field as obtained with routine use, and 0.35 µm resolution is attainable under more limited conditions. By reducing the numerical aperture, 0.8 µm resolution can be obtained over a 20 mm field with large depth of focus. This paper reports on recent system improvements and discusses the technical issues associated with short wavelength laser-based lithography.