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Summary form only given as follows. High-average-power, VUV incoherent light sources in the wavelength range 50-100 nm have potential use in advanced optical lithography applications, including the manufacture of next generation silicon chips. Sub 100 nm VUV lithography is a possible alternative to extreme ultraviolet (EUV) lithography (lambda~13.5 nm), as a future replacement for the current lithography standards based on ArF lasers (lambda=193 nm). We have characterised the VUV emission spectra from Ne2* excimers generated in a "windowless" high-pressure dielectric barrier discharge (DBD) source. Experiments were conducted using both AC (sinusoidal) and pulsed voltage power supplies to investigate efficiency issues for the production of the Ne2* 2nd continuum between 80-90 nm for a range of Ne pressures 0.1-1.0 bar and input electrical power loadings. The results show that the DBD source output is remarkably monochromatic with its observed spectral output in the ultraviolet consisting of only the principal Ne2* excimer emission band centered at 84 nm, and a weak H Lyman alpha line at 121.6 nm. Halpha line emission was observed due to the presence of trace H2 (or H2O) impurities that quench Ne2* species (and 84 nm output) via resonant Ne2*+H2 collisions. No other emission features were detected across the entire scanned VUV/UV range (30 nm-400 nm). Time-resolved signatures for the 1st/2nd Ne2* continua (75 nm/84 nm) were also recorded for different operating conditions. An important result from the experiments has been to show that pulsed voltage excitation substantially increases the electrical to VUV (84 nm) conversion efficiency by a factor 1.5times compared to AC excitation, for identical electrical power loadings. This jump in efficiency, for a Ne2* excimer lamp, has not been reported previously, as far as we are aware,- - and is consistent with our earlier experiments on Xe2* (lambda=172 nm) barrier discharge lamps.
Date of Conference: 15-19 June 2008