Laser-Assisted Atomic Layer Etching of Semiconductors and Nanomaterials

从晶圆表面去除层的蚀刻工艺在半导体工业中是普遍存在的。随着电子制造进入原子尺度，开发对尺寸可变性进行极其严格控制的蚀刻工艺势在必行。一种非常有前途的新兴方法是原子层蚀刻（ALEt）。结合激光照射可以控制并大大增强这一过程。该奖项支持研究激光辅助ALEt机制的基础研究。该研究有可能为在不损害邻近结构的情况下以单层精度调节目标材料尺寸提供手段。激光诱导的ALEt将最小化纳米结构材料的尺寸变化，从而保持加工序列的保真度。该项目的成果有可能通过实现原子电子时代的关键应用来推进纳米制造。因此，这项工作的成果将有利于美国的经济和社会。该研究涉及多个学科，包括激光化学加工、电子纳米制造、材料科学和在线过程诊断。耦合材料加工和表征方法将为本科生和研究生提供重要的和目前无法获得的机会，让他们在纳米科学和工程方面获得令人兴奋的研究经验和最先进的培训，并强调未被充分代表的群体的参与。激光辅助化学蚀刻可以利用连续的自限制反应来控制超薄层材料的去除。表面处理实验与分析诊断的结合填补了对ALEt机制（包括气相和表面反应）的化学和物理方面理解的科学空白。本研究将利用紫外激光源在不同压力和流速下研究前驱体蚀刻气体的解离，并测量所产生自由基的浓度与表面覆盖率之间的关系。在不同的入射辐照波长、脉冲持续时间和能量密度下，研究激光诱导激发靶材料和被吸附原子对原子层去除的影响。激光辅助的ALEt概念将扩展到通过尖端纳米图案完成过渡金属二硫化物（TMDC）薄膜和石墨烯的逐层蚀刻。在线光谱学将探索激光诱导解离过程的机制，加工激光与目标材料的耦合以及解吸过程。ALEt的激光激活也将被探索作为一种手段，建立一个低温蚀刻工艺兼容和互补的等离子体介导的过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Etching processes for removal of layers from the surface of wafers are ubiquitous in the semiconductor industry. As the electronics manufacturing enters the atomic scale regime, it is imperative to develop etching processes that offer extremely tight control of the size variability. A highly promising emerging approach to this end is the Atomic Layer Etching (ALEt). Incorporation of laser irradiation can control and substantially enhance this process. This award supports fundamental research to investigate the mechanisms of laser-assisted ALEt. The research has the potential to provide the means to regulate the target material dimensions with monolayer accuracy without inflicting damage on the neighboring structures. The laser-induced ALEt will minimize changes in the dimensions of nanostructured materials, thereby preserving the fidelity of the processing sequence. The project outcome has the potential to advance nanomanufacturing by enabling key applications in the atomic electronics era. Therefore, results from this work will benefit the U.S. economy and society. The research involves multiple disciplines, including laser chemical processing, electronics nanofabrication, materials science, and on line process diagnostics. The coupled materials processing and characterization methodology will provide significant and presently unavailable opportunities for undergraduate and graduate students to have exciting research experiences and state-of-the-art training in nanoscience and engineering with emphasis on the participation of underrepresented groups. Laser-assisted chemical etching can control the removal of an ultra-thin layer of material using sequential self-limiting reactions. The combination of surface processing experiments with analytical diagnostics bridges a scientific gap in the understanding of chemical and physical aspects of the ALEt mechanisms including gas phase and surface reactions. The research will examine the dissociation of precursor etchant gases by applying ultraviolet laser sources under different pressures and flow rates, measure and correlate the concentrations of the produced radicals to the surface coverage. Work will be conducted to investigate the effect of laser-induced excitation of the target material and the adsorbed atoms on the atomic layer removal under different incident irradiation wavelengths, pulse durations and energy densities. The laser-aided ALEt concept will be extended to accomplish layer-by-layer etching of transition metal dichalcogenide (TMDC) films and graphene via tip-based nanopatterning. On line spectroscopy will probe the mechanisms of the laser-induced dissociation process, the coupling of the processing laser to the target material and the desorption process. The laser activation of ALEt will also be explored as a means to establish a low temperature etching process compatible and complementary to plasma-mediated processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.