Micowave plasma-assisted ionization of sputtered aluminum atoms in DC magnetron sputtering

DC magnetron sputtering was carried out using a microwave plasma to enhance the ionization of sputtered aluminum atoms at a low gas pressure. The ionization fraction of sputtered aluminum atoms measured using a gridded thickness monitor was 40% at a low gas pressure of 0.05 Pa. The collision frequency for the ionization of sputtered aluminum atoms calculated theoretically under the assumption of electron-impact ionization was in good agreement with the experimental results.