A dry-cleaning technique-consisting of down-flow plasma and utilizing gas-flow viscosity-has been developed. This technique is expected to be used for particle cleaning during semiconductor manufacturing. Particles are removed by both the chemical effects of the plasma and the mechanical effects of the viscous friction of the gas flow. Regarding the mechanical effects, the viscous friction is increased by narrowing the gas-flow space along the wafer surface. As for chemical effects, fluorine radical relaxes the adhesion force of particles on the silicon wafer. It has been experimentally found that the removal efficiency of Al2O3 particles on a Si wafer is 98% in 60 s and the etching depth of polysilicon is 0.17 nm. It has been also found that the technique causes no charge-buildup damage. (C) 2004 American Vacuum Society.