Surface processing with high-energy gas cluster ion beams

Gas cluster ion beams can produce high rate sputtering with low damage compared with the more familiar monomer ion beam process. In order to realize high-speed surface processing, a high-energy gas cluster ion beam irradiation system was developed in which high-energy Ar cluster ion beams were generated. The mean size of the Ar cluster was about 1800 atoms, as measured using the time-of-flight (TOF) method. Si substrates were irradiated with the Ar cluster ions at acceleration energies between 20 and 80 keV. The sputtering yield increased with acceleration energy and reached about 230 atoms/ion at 80 keV, a value about 180 times higher than that of Ar monomer ions. Au films were also irradiated at acceleration energies between 20 and 80 keV and the surfaces were observed with Atomic Force Microscopy (AFM). The high-energy cluster ion irradiation caused a decrease in surface roughness. These results indicate that high-speed smooth etching can be realized with high-energy cluster ion beams. This processing method can be applied to fabricate nano-devices.