Etching of metallic materials with Cl2 gas cluster ion beam

Cluster ion beam processes exhibit high rate sputtering with low damage, and in particular, extremely high sputtering rates are expected using reactive cluster ion beams. Si could be sputtered at extremely high rates using reactive cluster ion beams, such as SF6, Cl2, CF4, CHF3, and CH2F2. However, processing of metallic materials with reactive cluster ion beams has not been studied yet. It was expected that high-speed etching of metallic materials can be realized with Cl2 cluster ion irradiation, because such a beam would reactively sputter these materials. We generated a Cl2 cluster ion beam and investigated the etching characteristics of various metallic materials, such as Ni and Al films, under this irradiation. The size of the Cl2 cluster, as measured with a time-of-flight (TOF) system, was about 1400 molecules. The sputtering yield for each metal was more than 10 times higher than that obtained with Ar cluster ions, showing that Cl2 cluster ion irradiation reactively sputtered the metallic materials. These results indicated that Cl2 cluster ion irradiation was suitable for high-speed processing of metallic materials.