A high ionization efficiency source for partially ionized beam deposition

Abstract

The design and testing of a high ionization efficiency source for a partially ionized beam deposition (PIBD) system are described. The vaporized material from a crucible is partially ionized at the crucible exit, where the vapor has its highest density. The system can provide ionization efficiencies of up to 5% (ion/atom ratio) at ion energies ranging from 0.2 to 6 keV. Measurements of the ion current versus substrate bias potential along with the deposition rate are reported using Al as source material. A uniform ion beam intensity has been obtained over a 6-cm-diam substrate at a distance of 30 cm above the source. If the ionization source is placed a few centimeters away from the crucible, as it is in the conventional PIBD design, the ionization efficiency would reduce to <0.2% (ion/atom ratio). The reduction can be easily explained by geometry consideration.