MEMS LMIS Chips: Investigation of Wetting and Operational Stability of Liquid Metal Ion Sources based on Glass Substrates

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A Liquid-Metal-Ion-Source usually consists of a metal-based emitter such as a sharp tungsten needle wetted by a liquid metal propellant. By applying a high voltage between the emitter and a hole extractor, ion beams in the range of a few tens of µA can be generated. Such ion sources are widely used in Focused Ion Beam machines for ion implanting, lithography or micro/nano manufacturing. Recently, we showed that in principle also glass substrates can be used for the emitter structure which would allow much smaller capillaries compared to metal-based emitters that in turn enables highly efficient and controllable ion sources. Moreover, glass substrates could enable MEMS emitter structures that could allow easily scalable Liquid Metal Ion Sources with high currents that are otherwise not easily attainable. First experiments showed that bonding between glass substrates and liquid propellants must be enhanced to allow long term and stable operation. We propose a thorough investigation of the bonding strengths between various glass substrates and different liquid metal propellants under different circumstances. For example we want to test bonding with oxide-free propellants in an oxide free environment using a glove box. After understanding and optimising the substrate and propellant candidates, a single glass emitter shall be made and tested for Long term stability. Next, a cluster of single glass emitters shall be tested in order to characterise their homogeneity and to investigate any issues related to clustering which can be important for very large clusters. At last, real MEMS prototypes shall be designed, manufactured and tested. For this task, we propose a strong cooperation with the institute for semiconductors and microsystems at TU Dresden which provides all facilities and expertise for MEMS systems. This would lead to a novel new type of ion source (glass LMIS) that has potentially superior properties like high scalability and stability, as well as a better understanding of the bonding between liquid metals on glass-like substrates in general. A MEMS LMIS would be very interesting for micro propulsion systems e.g. on nanosatellites or formation flying, as well as for self healing high current electron sources or large array ion implantation with high processing speeds among others.