Low-damage etching of poly-Si and SiO2 via a low-energy electron beam in inductively coupled CF4 plasma

Abstract Electron-assisted etching of poly-Si and SiO 2 is performed via a grid system in inductively coupled CF 4 plasma. The feasibility of electron-assisted etching is discussed with a focus on the low-surface damage of the etching. The etch rate increases with electron beam energy, which indicates that the electrons assist the surface etching process. To verify this, etching of poly-Si and SiO 2 is performed in several plasma conditions, which leads to differences in etch rate that depend on the presence or absence of radicals and electron beams. Poly-Si and SiO 2 are not etched without radicals of CF 4 plasma, but they are etched when such radicals are present. When the electron beam and radicals exist simultaneously, the etch rate increases more dramatically than in the case of a CF 4 plasma without an electron beam, demonstrating that the electron beam assists the etching process. Optical emission spectroscopy is employed to verify the F radical does not affect the etch rate increase. The surface roughness is measured after electron-assisted etching and compared with the surface roughness after ion-assisted etching.