1 July 2002 Verification studies of thermophoretic protection for EUV masks
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Abstract
A 'thermophoretic pellicle' has been proposed as an alternative to the traditional organic pellicle as a means of protecting EUV lithographic photomasks from particle contamination. The thermophoretic pellicle protects a mask from particles by exploiting the thermophoretic force, which is exerted on a particle by a surrounding gas in which a temperature gradient exists. Two critical requirements of the thermophoretic pellicle are: 1) the mask is kept warmer than its surroundings (either by heating the mask or by cooling the surroundings) and 2) the surrounding gas pressure is kept sufficiently high to enable thermophoretic protection. Experiments are presented which verify the viabilitiy of thermophoretic protection for EUV masks under model conditions. In these experiments, wafers are exposed to monodisperse polystyrene latex (PSL) spheres under carefully controlled experimental conditions. Robust thermophoretic protection is observed over a wide range of argon gas pressures (50-1600 mTorr or 6.66-213 Pa), particle sizes (65-300 nm), and temperature gradients (2-15 K/cm).
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Daniel J. Rader, Daniel J. Rader, Daniel E. Dedrick, Daniel E. Dedrick, Eric W. Beyer, Eric W. Beyer, Alvin H. Leung, Alvin H. Leung, Leonard E. Klebanoff, Leonard E. Klebanoff, } "Verification studies of thermophoretic protection for EUV masks", Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); doi: 10.1117/12.472288; https://doi.org/10.1117/12.472288
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