Silicon wafer cleaning using new liquid aerosol with controlled droplet velocity and size by rotary atomizer method

A liquid aerosol, which sprays cleaning liquid with a carrier gas, is widely used for cleaning semiconductor devices. The liquid aerosol using a conventional two-fluid nozzle may cause pattern damage on the wafer. To resolve this problem, we have made a prototype new rotary atomizing two-fluid cleaning nozzle (RAC nozzle), which can control the velocity distribution and size distribution of flying liquid droplets separately. It was confirmed by measuring flying liquid droplets using a shadow Doppler particle analyzer system that the mean volumetric diameter of the droplets could be atomized to 20 μm or less at a rotational speed of the air turbine of 50,000 min^-1 and that the mean velocity of the flying liquid droplets could be controlled in the range under 65 m/s independently. It was confirmed in a cleaning experiment using polystyrene latex (PSL) particles on a wafer that particle removal efficiency increased when shaping air pressure increased. Also, the particle removal efficiency was improved with the finer atomization promoted by a higher rotational speed of the air turbine.