Hydrogen Plasma Exposure of Polymethylmethacrylate and Etching by Low Energy Ar⁺ Ion Beam

Abstract

  Effects of hydrogen plasma exposure in polymer dry etching processes have been investigated with a low-energy mass-selected ion beam system. In the present study, we use a spin-coated polymethylmethacrylate (PMMA) film on a quartz crystal microbalance as a model polymer. The surface modification of the PMMA film by the hydrogen plasma exposure in an inverter plasma system was investigated by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. XPS results show that oxygen atoms were preferentially sputtered from the PMMA film by the hydrogen plasma exposure. Spectroscopic ellipsometry results show that depth of the modified layer of the hydrogen plasma exposed PMMA film was about 40 nm. Etching yields of the pristine PMMA film and the hydrogen plasma exposed PMMA film by 470 eV Ar⁺ ion beam injections were measured. It is found that the etching yield of the hydrogen plasma exposed PMMA film was about half of that of the pristine PMMA film.