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

液态金属离子源通常由金属发射器组成，例如被液态金属推进剂润湿的锋利的钨针。通过在发射器和空穴萃取器之间施加高电压，可以产生几十微安范围的离子束。这种离子源被广泛用于离子注入、光刻或微/纳米制造的聚焦离子束机器中。最近，我们发现，原则上也可以使用玻璃衬底作为发射器结构，与金属发射器相比，这将允许更小的毛细管，从而实现高效和可控的离子源。此外，玻璃基板可以实现MEMS发射器结构，使其能够轻松扩展具有大电流的液态金属离子源，否则难以获得。最初的实验表明，必须加强玻璃基板与液体推进剂之间的结合，才能长期稳定地运行。我们建议深入研究不同玻璃基板与不同液体金属推进剂在不同环境下的结合强度。例如，我们希望使用手套箱在无氧化物环境中测试与无氧化物推进剂的结合。在了解和优化了基片和推进剂候选后，应制造一个单一的玻璃发射器并进行长期稳定性测试。接下来，应该测试一组单一玻璃发射体，以确定它们的同质性，并调查与聚集有关的任何问题，这对非常大的聚集可能是重要的。最后，设计、制造和测试真实的MEMS样机。对于这项任务，我们建议与德累斯顿理工大学半导体和微系统研究所进行强有力的合作，该研究所为MEMS系统提供所有设施和专业知识。这将导致一种新型的离子源(玻璃LMI)，它具有潜在的优越性能，如高可扩展性和稳定性，以及更好地了解一般玻璃基板上液态金属之间的结合。MEMS LMI对于微推进系统，例如在纳米卫星或编队飞行中，以及在具有高处理速度的自愈大电流电子源或大阵列离子注入等方面将非常有意义。

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.