Removal of 10-nm contaminant particles from a wafer surface with supersonic CO2 particle beam

Contaminant control is becoming a major issue of nanoscale device. Cryogenic aerosol beam using micron-sized aerosol particles has long been successfully used to remove contaminant particles (CPs) down to 50nm, and supersonic particle beam using particles smaller than 100nm lowered the limit of cleaning down to 20nm size. In this study, the supersonic particle beam technique that uses nanometer-sized bullet particles moving at supersonic velocity was improved and successfully used to remove 10-nm CPs. Nanometer-sized bullet particles were generated by gas phase nucleation and growth using CO2/He. Cleaning performance for 10nm contaminant particle was sensitive to the combined condition of the beam particle size and velocity. The velocity of the nanobullets was the most important factor for the removal efficiency of CPs, and the use of light carrier gas was very effective in increasing particle velocity. Also, the cleaning performance is closely related with chamber pressure, improving at a lower chamber pressure. The best cleaning efficiency was about 95% for 10nm Al2O3 particle, which was the best performance reported to date.