(Invited) Reactions on Metal Surface and Diketone Induced By Gas Cluster Ions during Atomic Layer Etching

Abstract

Gas cluster ion beams (GCIB), which consists of several thousands of gaseous atoms or molecules, have been used as novel low-energy ion beams for surface processing and analysis. Since thousands of low-energy (several eV) atoms bombard a surface at the same time and the same position, the bombarded area experiences transient high-temperature and high-pressure conditions, which enhance sputtering of atoms or enhance surface reactions. In recent years, we have been investigating to apply GCIB as energetic ions for atomic layer etching. We have reported ALE of transition metals (Cu and Ni) with GCIB irradiations and diketone (acetylacetone and hexafluoroacetone). We separated each etching step as following; (1) adsorption of diketone molecules on metal oxide, (2) evacuation of residual vapor, (3) irradiation of oxygen GCIB to remove metal oxide. By using 5 keV oxygen GCIB (~ 2eV/molecules), thin layer of nickel oxide with adsorbed acetylacetone is removed. There is no physical sputtering at this energy region, which realizes self-limiting ALE process. From in-situ XPS study, Ni oxide with adsorbed diketone molecules can be removed by Ar-GCIB irradiation. It means that other oxidation method can be used to form metal oxide, and Ar-GCIB can be used for the removal steps. In this talk, we will report surface reactions between metals and diketone induced by gas cluster ion irradiations, and etching characteristics of various metals using GCIB irradiation and diketone.