Material Processing with Broad-Beam Ion Sources

Abstract

During the past two decades, ionized gases have been increasingly applied to etching, modification, and deposition of materials in thin film form (1), often using radio frequency (rf) excited plasmas. In parallel, the technology of broad-beam, multi aperture ion sources has been extensively developed for space propulsion (2). Only in the past few years have these broad-beam ion sources been applied in a systematic fashion to materials problems. The purpose of this review is to describe the growth ofthis new area of ion beam processing of materials. To define the field more precisely, the ion beams referred to here are typically several cm to tens of cm in diameter, not mass­ separated, with ion energies of tens of eV to a few keY. Not included are finely focused ion beams for surface analytical studies; ion implantation and ion-mixing beams; ion beams for fusion injection; and single-aperture beams. The primary advantage of ion beam processing of materials lies in the control available with an ion beam as compared to other plasma processes. The ion flux and ion energy are easily measured and independently controlled, and the direction of ion impact on surfaces is controlled, since the beams operate in a low background gas pressure of typically 0.01 Pa. This review begins with a description of broad-beam multiaperture ion sources, emphasizing the design advances that have stimulated recent