The development of surface topography using two ion beams

Abstract

Ion etching is a well-established technique for the micromachining of solid surfaces. It is used extensively in surface analysis with techniques such as Auger electron spectroscopy, ESCA and SIMS, both for surface cleaning and composition—depth profiling. In all of these applications the formation of ion-induced surface topography is a serious problem. Experimental evidence has shown that the use of two ion guns symmetrically inclined about the surface normal can partially ameliorate this difficulty. This paper considers the problem theoretically and shows for model systems the type of topography produced by two guns for various angles of separation. In general, the use of two guns suppresses cone formation and leads to the development of flatter-topped structures. Two guns also tend to undercut impurities which would otherwise lead to massive cone formation using one ion gun. The analysis lends further support to the use of twin ion beams for optimum sputterdepth profiling in surface analysis.