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基发射器组成，如被液态金属推进剂浸湿的尖锐钨针。通过在发射器和空穴提取器之间施加高压，可以产生几十µa范围内的离子束。这种离子源广泛应用于离子注入、光刻或微纳米制造的聚焦离子束机器中。最近，我们表明，原则上玻璃基板也可以用于发射器结构，与金属基发射器相比，它允许更小的毛细血管，从而实现高效和可控的离子源。此外，玻璃基板可以实现MEMS发射极结构，可以轻松扩展具有高电流的液态金属离子源，否则不容易实现。第一个实验表明，必须加强玻璃基板和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态金属推进剂在不同情况下的结合强度。例如，我们想用手套箱在无氧化物环境中测试与无氧化物推进剂的粘合。在了解和优化衬底和候选推进剂后，应制作一个单一的玻璃发射器并测试其长期稳定性。接下来，应测试一组单个玻璃发射器，以表征其均匀性，并调查与群集相关的任何问题，这对于非常大的群集可能很重要。最后，设计、制造和测试真正的MEMS原型。为此，我们建议与德累斯顿工业大学的半导体和微系统研究所进行强有力的合作，该研究所提供MEMS系统的所有设施和专业知识。这将导致一种新型离子源（玻璃LMIS），它具有潜在的优越性能，如高可扩展性和稳定性，以及更好地理解一般玻璃状基底上液态金属之间的键合。MEMS LMIS对于微推进系统非常有趣，例如在纳米卫星或编队飞行上，以及自修复高电流电子源或具有高处理速度的大阵列离子注入等。

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.