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一个金属发射体组成，例如一个被液态金属推进剂润湿的尖锐钨针。通过在发射器和空穴提取器之间施加高电压，可以产生几十μA范围内的离子束。这种离子源广泛用于离子注入、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，这将允许更小的毛细管，这反过来又能够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，其可以允许容易地可扩展的具有高电流的液态金属离子源，否则不容易获得。第一次实验表明，玻璃基板和液体推进剂之间的结合必须得到加强，以允许长期和稳定的操作。我们建议彻底研究不同情况下各种玻璃基底与不同液态金属推进剂之间的结合强度。例如，我们想在手套箱中测试无氧化物推进剂在无氧化物环境中的结合。在了解和优化基质和推进剂候选物后，应制造单个玻璃发射器并对其进行长期稳定性测试。接下来，应测试单个玻璃发射器的集群，以验证其均匀性并研究与集群相关的任何问题，这对于非常大的集群可能很重要。最后，设计、制造和测试真实的MEMS样机。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密切合作，该研究所为MEMS系统提供所有设施和专业知识。这将导致一种新颖的新型离子源（玻璃LMIS），其具有潜在的上级性质，如高可扩展性和稳定性，以及更好地理解通常在玻璃状基板上的液体金属之间的结合。MEMS LMIS对于例如纳米卫星或编队飞行上的微推进系统以及对于具有高处理速度的自修复高电流电子源或大阵列离子注入等将是非常令人感兴趣的。

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.