Silicon-oxide (SiO2) etching employing an electron-beam-excited plasma has been investigated. SiO2 films were etched using self-bias induced by the electron beam for the generating plasma. As a source gas, the CF4 diluted by Ar (CF4/Ar) was employed. The etch rate of 117 nm/min has been obtained at a total pressure of 0.18 Pa and a total flow rate of 43 sccm with a CF4/Ar flow rate ratio of 13%. The etching was carried out at an electron-beam current of 9.5 A and an electron-acceleration voltage of 100 V without any additional bias power supply. The CF4/Ar plasma diagnostics was carried out by using a Langmuir probe and optical-emission spectroscopy. It has been found that the higher electron-beam current for generating plasmas improves the plasma density and sheath potential, resulting in a higher etch rate Of SiO2. The results indicate that the electron-beam-excited plasma has a potential for application to micromachining processes. (C) 2004 American Vacuum Society.