Interactions of ethanol cluster ion beams with silicon surfaces

The liquid cluster ion beam system was developed, in which cluster ions of organic molecules such as ethanol could be produced. In order to investigate the interactions of ethanol cluster ion beams with solid surfaces, SiO2 substrates and SiO2 films were irradiated at different acceleration voltages. The sputtered depth increased exponentially with the acceleration voltage. When the acceleration voltage was 9 kV, the sputtered depths of Si and SiO2 at a dose of 1 x 10(16) ions/cm(2) were 344.6 nm and 47.2 nm, respectively. The sputtering yield for the Si surface was approximately 100 times larger than that by Ar ion beams. With regards to the sputtering ratio Of Si to SiO2, the ratio increased with decreasing acceleration voltage. This suggests that chemical reactions between Si and ethanol produced silicon hydride which was the dominant etching material for the Si surfaces. In addition, the AFM observation showed that the sputtered surface had an average roughness of less than I nm. With regards to the crystalline state of the sputtered surface, the RBS and ellipsometry measurements were performed, and they showed that the Si surface damage induced by ethanol cluster ion irradiation was less than that by Ar monomer ion irradiation. Thus, Si surfaces etched at high sputtering speed by ethanol cluster ion beams had a lower damage and an atomically flat surface. (c) 2005 Elsevier B.V. All rights reserved.