High-speed processing with Cl2 cluster ion beam

Abstract

Cluster ion beam processes can produce high rate sputtering with low damage compared with monomer ion beam processes. Cl2 cluster ion beams with different size distributions were generated with controlling the ionization conditions. Size distributions were measured using the time-of-flight (TOF) method. Si substrates and SiO2 films were irradiated with the Cl2 cluster ions at acceleration energies of 10–30keV and the etching ratio of Si/SiO2 was investigated. The sputtering yield increased with acceleration energy and was a few thousand times higher than that of Ar monomer ions. The sputtering yield of Cl2 cluster ions was about 4400atoms/ion at 30keV acceleration energy. The etching ratio of Si/SiO2 was above eight at acceleration energies in the range 10–30keV. Thus, SiO2 can be used as a mask for irradiation with Cl2 cluster ion beam, which is an advantage for semiconductor processing. In order to keep high sputtering yield and high etching ratio, the cluster size needs to be sufficiently large and size control is important.