Paper PS-TuP9
Si, SiO₂, and Si₃N₄ Etching Characteristics of Silicon Halide Ions (SiF_x⁺, SiCl_x⁺, and SiBr_x⁺)

Tuesday, October 31, 2017, 6:30 pm, Room Central Hall

Reactive ion etching (RIE) by halogen-based plasmas is widely used for etching of silicon-based materials such Si, SiO₂, and Si₃N₄ in semiconductor manufacturing processes. As semiconductor devices continue to be miniaturized, a better understanding of basic reactions of etching and/or deposition processes on substrate surfaces has become more important than before for finer controls of device structures in the manufacturing processes. In etching processes of silicon-based materials by halogen-based plasmas, Si atoms desorbed from the surface as etching products may enter the plasma (as ions such as SiBr_x⁺ or charge neutral radicals such as SiBr_x) and return to the surface, forming an additional silicon-based material layer on the substrate as well as hard mask materials (such as SiO₂, and Si₃N₄). Therefore it is important to clarify etching characteristics of silicon-halides ions for Si, SiO2, and Si3N4 substrates for the development of highly controllable etching processes with halogen-based plasmas. Beam experiments of such etching processes offer useful information for a better understanding of interactions of individual species contained in a plasma with the surface. In this study, etching and/or deposition reactions of Si, SiO₂, and Si₃N₄ substrates are examined with the use of a mass-selected ion beam system, which can clarify the roles of silicon (Si⁺), halogen (F⁺, Cl⁺, and Br⁺), silicon mono-halide (SiF⁺, SiCl⁺, and SiBr⁺), and silicon tri-halide (SiF₃⁺,SiCl₃⁺, and SiBr₃⁺) ions for etching of Si-based materials. Si+ irradiation below 1000eV deposits silicon atoms on Si, SiO₂, and Si₃N₄ surfaces. Similarly, at sufficiently low incident energy, a silicon mono-halide ion beam also deposits silicon on the surface. The etching yield by silicon tri-halide ions is typically larger than three times the etching yield by single-halogen ions. Experimentally obtained etching yields or deposition rates for various combinations of Si-based substrates and incident silicon halides as functions of incident ion energy offer critical information for the further development of highly precise etching processes.