Removal of 10-nm contaminant particles from Si wafers using argon bullet particles

Removal of nanometer-sized contaminant particles (CPs) from substrates is essential to successful fabrication of nano scale devices. But the cleaning limit of various current technologies stay around 50 nm. Cryogenic aerosol beam has long been successfully employed to remove CPs down to 50 nm, and supersonic particle beam using particles smaller than 100 nm lowered the limit of cleaning down to 20 nm size. In this study, the particle beam technique that uses nanometer-sized bullet particles moving at supersonic velocity was improved, and successfully employed to remove contaminant particles as small as 10 nm. Ar nano-bullets of about 20-50 nm were generated by gas-phase nucleation, and growth in a supersonic nozzle: appropriate size and velocity of the nano-bullets were obtained by optimizing the Ar/He mixture fraction and nozzle contours. Cleaning efficiency > 95% was attained. Nano-bullet velocity was found to be the most important parameter affecting removal of contaminant particles in the 10-nm size range.