RF-plasma-assisted fast atom beam etching

A fast atom beam (FAB) source used for dry etching is capable of high anisotropy etching because it utilizes neutral etching species. However, the kinetic energy of the FAB is high (normally above 1 keV), therefore, selectivity is diminished due to the spattering effect of the atom beam; also, etching damage is caused on the surface of the sample specimen. We propose and have fabricated a radio-frequency (RF) plasma-assisted FAB source, which can produce a low-energy FAB. A conventional FAB source generates plasma inside a cathode tube by applying a high voltage between the cathode and an anode situated in the tube. The energy of the FAB is almost proportional to the anode voltage. The new FAB source consists of a conventional FAB source and a helicon plasma cell to assist the generation of plasma and increase the plasma density in the cathode tube. Therefore, plasma is generated at a relatively low voltage (from 50 V to 1 kV). Using this FAB source, the preliminary performance, such as the etching rate and the damage caused on the silicon surface, is investigated.