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).© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.