Ion sources for nanofabrication and high resolution lithography

Ion sources that are used to produce nanometer resolution patterns directly on the substrate are either point sources or volume plasma sources. The point sources are used in focused ion beam systems which focus an image of the point on the sample. These sources are, in practice gallium liquid metal. Other sources, such as gas field ion sources, are also being considered. Volume plasma sources are used with ion projection, where instead of the image of a point source, the image of a "back illuminated" stencil mask is projected on the substrate. The operation, application, and characteristics of the three types of sources are reviewed and compared.