Effects of ionization power on ion energy distribution in ionized rf sputtering measured by an energy-resolved mass spectrometer

In an ionized sputtering technique, it is crucial to give a proper energy to the particles in order to improve film properties or to enhance directionality of the sputtered particles without causing disorder or other undesired damages to the growing film. In this study, ion energy distribution has been investigated by an energy-resolved mass spectrometer for ionized Ti sputtering in order to discuss effects of coil r.f. power and magnetron cathode r.f. power on energy distribution of Ar+ and Ti+ ions arriving at the substrate. The cathode used in the experiment was a magnetron type with a 55-mm diameter Ti target. Ion energy distribution was measured by PPM-421 Plasma Monitor (Balzers) whose orifice to the ion analysis optics was set in front of the sputtering cathode with a distance of 200 mm. The coil r.f power and the cathode r.f. power were varied up to 200 W. The experimental results show that energy distribution of Ti+ ions was enhanced from a few tens of eV to more than 100 eV as the coil r.f. power increased. The energy increase of Ti+ ions by an r.f. coil plasma was more drastic for a lower cathode r.f. power. As the cathode r.f. power increases, the energy of Ti+ ions decreased, as a result of quenching of the r.f. coil plasma. The quenching is thought to be induced by the increase in the number of Ti atoms passing through the r.f. plasma region. Energy distribution of Ar+ ions showed similar tendency to that of Ti+ ions. (C) 1998 Elsevier Science S.A. All rights reserved.