High brightness point ion sources using liquid ionic compounds

Abstract

A novel high brightness point ion source (10) that is adapted to operate with liquid ionic compounds such as mixtures of molten salts, bases or acids. The ion source is basically comprised of two parts: the needle assembly (11) and the extraction assembly (12). The former consists of a point shaped needle (13) made of a refractory ceramic material, whose sharpened extremity is referred to as the tip (13a). The needle is partially lodged in a recess of an insulating support (15). A heating coil (14) made of stainless steel is tightly wound around a portion of the needle adjacent to the tip. The needle is coated with the mixture, for instance, by dipping in a crucible containing the mixture. The extraction assembly is comprised of a metal extracting electrode (20) provided with a central aperture that is screwed on a cylindrical metallic body (19), so that the spacing between the tip and the aperture center is adjustable. The needle assembly is mounted inside the cylindrical body and accurately affixed thereto by centering screws (22). The high brightness point ion source is then ready for use in a FIB column. A heating current supply (18) is connected to the coil extremities to melt the mixture if necessary. An extraction voltage supply (23) applies a potential difference between the extraction assembly and the mixture at the tip apex for ion emission.

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