Liquid Metal Alloy Ion Sources - an Alternative for Focused Ion Beam Technology

Today Focused Ion Beam (FIB) processing is nearly exclusively based on gallium Liquid Metal Ion Sources (LMIS). But, many applications in the µm- or nm range could benefit from ion species other than gallium: local ion implantation, ion beam mixing, ion beam synthesis or Focused Ion Beam Lithography (IBL). Therefore Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand remarkable the application fields for FIB. Especially the IBL process shows potential advantages over e.g. electron beam (EBL) or other lithography techniques: direct, resistless, and three-dimensional patterning, enabling a simultaneous in-situ process control by cross sectioning and inspection. Taking additionally into account that the used ion species influence significantly the physical and chemical nature of the resulting nanostructures -in particular the electrical, optical, magnetic and mechanic properties- leading to a large potential application area which can be tuned by choosing a well suited LMAIS. Nearly half of the elements of the Periodic Table are recently available in FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness and stable ion current. Recent developments could make these sources feasible for nano patterning issues as an alternative technology more in research than in industry. The authors will review existing LMAIS, working with pure elements (LMIS) other than Ga or binary or ternary alloys, their physical properties as well as the fabrication technology and prospective domains for modern FIB applications. Other emerging ion sources will be also presented and their performances discussed.