Cryogenic particle beam is an effective means of removing nano-sized contaminant particles from a substrate. To overcome the current cleaning limit of 50 nm, a particle beam with novel properties - smaller bullet size moving at a higher velocity - was used. Argon or Ar/He mixture was expanded through contoured Laval nozzles of various expansion angles to generate extremely small particles through genuine nucleation and growth. Argon particles smaller than 100 nm - smaller by a factor of 10 or more than the conventional Argon aerosols - were successfully generated, and could perfectly remove various ceramic particles down to 20 nm. (C) 2009 Elsevier B.V. All rights reserved.