Evolution of light source technology to support immersion and EUV lithography

Since the early 1980's, the resolution of optical projection lithography has improved dramatically primarily due to three factors: increases in projection lens numerical aperture, reduction of the imaging source wavelength, and continued reduction of the k1 factor. These three factors have been enabled by the concurrent improvements in lens making technology, DUV light sources, photoresist technology, and resolution enhancement techniques. The DUV light source, excimer KrF and ArF lasers, has entered main stream production and now images more than 50% of the critical layers in today's leading-edge devices. Looking forward to both immersion lithography and beyond to EUV lithography, new light source technologies must be created to enable the continued progression of shrinking feature sizes embodied by Moore's law.