Functional extension and upgrade of a reactive ion etching tool

利用所要求的资金，物理系洁净室的反应离子刻蚀系统将升级，采用感应耦合等离子体激发。电感耦合等离子体技术允许离子和等离子体密度的独立调节。通过这种方式，可以非常精确地控制刻蚀过程，这是当前许多研究项目不可或缺的。升级的关键项目之一是对范德华异质结构的研究。例如，它将允许制造样品，从而能够研究双层石墨烯中的脆弱分数量子霍尔效应。此外，还计划进行实验来研究具有扭曲层的2D材料的电子结构。一个目标是更好地理解在扭曲的石墨烯双层中观察到的超导状态。为了揭示这种范德华异质结构的内在性质，必须防止与衬底的任何相互作用。这可以通过将功能层封装在绝缘氮化硼中来实现。对于这一过程，精确控制刻蚀速率的电感耦合等离子体模式是必不可少的。此外，感应耦合等离子体模式还允许高纵横比、高形状保真度和低边缘粗糙度的纳米结构刻蚀，这对于用于相干X射线成像的X射线光学领域来说是至关重要的，以便在多尺度上研究生物系统的结构。在这一点上，等离子体技术的应用对于衍射光学的进一步发展和实现能够在低功率下产生纳米焦点的纳米结构X射线阳极来说是至关重要的。最终，该小组计划展示新概念“芯片上的X射线光学”，该概念旨在实现新颖的泵浦探测、干涉、层析和X射线量子光学实验。升级后的等离子体工具的另一个用途是研究固体和纳米结构中的超快现象，它将允许开发和应用合适的光谱、显微镜和衍射技术。为此，需要非常紧凑的电子光学器件。计划在应用的刻蚀模式下，使用光刻工艺和深反应离子刻蚀相结合的方式来制造下一代电子光学器件。

With the requested funding, the Reactive Ion Etching System in the cleanroom of the Faculty of Physics will be upgraded with the option of inductively coupled plasma excitation. The inductively coupled plasma technology allows an independent adjustment of the ion and the plasma density. In this way, the etching process can be controlled very precisely, which is indispensable for many current research projects. One of the projects that the upgrade is critical for is the investigation of van-der-Waals heterostructures. For example, it will allow to fabricate samples that allow to investigate the fragile fractional quantum Hall effect in bilayer graphene. Additionally, experiments are planned to investigate the electronic structure of 2D materials with twisted layers. One goal is to gain a better understanding of the superconducting state which has been observed in twisted graphene double layers. In order to reveal the intrinsic properties of such van der-Waals heterostructures, any interaction with the substrate must be prevented. This can be achieved by encapsulating the functional layers in insulating boron nitride. For this process, the inductively coupled plasma mode with a precise control of the etching rate is absolutely essential. Moreover, the inductively coupled plasma mode also allows nanostructure etching with high aspect ratio, high shape fidelity and low edge roughness which is critical for the field of X-ray optics for coherent X-ray imaging in order to investigate the structure of biological systems on multiple scales. At this point, the applied for plasma technology is crucial for the further development of diffractive optics and for the realization of nanostructured X-ray anodes, which can generate a nano-focus at low power. Ultimately, the group plans to demonstrate the new concept "X-ray Optics on a Chip", which is intended to realize novel pump-probe, interferometric, tomographic and X-ray quantum optical experiments. A further use case for the upgraded plasma tool is the investigation ultrafast phenomena in solids and nanostructures where it will be allow the development and application of suitable spectroscopy, microscopy and diffraction techniques. For this purpose, extremely compact electron optics are required. It is planned to fabricate next-generation electron optics using lithographic processes in combination with deep reactive ion etching in the applied for etching mode.