HIGH-RESOLUTION FOCUSED ION-BEAMS

The technology of high-resolution focused ion beams has advanced drama tically in the past 15 years as focusing systems have evolved from lab oratory instruments producing minuscule current densities to high curr ent density tools which have sparked an important new process: direct micromachining at the micrometer level. This development has been due primarily to the exploitation of field emission ion sources and in par ticular the liquid-metal ion source. Originally developed in the early 1960's as a byproduct of the development of electrostatic rocket engi nes, the liquid-metal ion source was adapted for focused beam work in the late 1970's, when it was demonstrated that submicrometer focused i on beams could be produced with current densities greater than 1 A cm- 2. Ions can be produced with liquid-metal ion sources from elements in cluding Al, As, Au, B, Be, Bi, Cs, Cu, Ga, Ge, Fe, In, Li, P, Pb, Pd, Si, Sn, and Zn. In the past decade, focused ion beam systems with liqu id-metal ion sources have had a significant impact on the semiconducto r industry as they were applied to new and greatly improved methods of failure analysis, as well as circuit repair and modification, in situ processing, and lithographic mask repair. This article discusses fiel d emission ion sources, high-resolution ion focusing systems, and mean s for analyzing their performance. A number of technologically interes ting and useful applications are also discussed.