Fundamental Study on the Etching Mechanics of Metal-Assisted Chemical Etching of Silicon for 2D and 3D Nanomanufacturing Applications

提出的研究旨在了解金属辅助硅化学蚀刻（MaCE）中催化剂运动的基本机制。MaCE是一种新的方法，可以蚀刻复杂的2D和3D形状，如地下摆线和3D螺旋结构，同时即使在宽高比为50:1的情况下也能保持1 nm左右的紧密特征分辨率。当硅被催化剂上的电反应蚀刻时，定义蚀刻轮廓的金属催化剂会进入硅中，从而在整个蚀刻长度内保持蚀刻轮廓，并通过控制催化剂运动来蚀刻3D结构。虽然MaCE的化学计量化学已经合理地建立，但涉及粒子运动的基本动力学和力仍然未知和未研究。本研究将研究蚀刻剂组成、催化剂形状、催化剂组成和外场如何影响MaCE的动力学和力，以确定蚀刻速率、分辨率、形貌和方向。此外，还将开发电场、力、催化剂运动和蚀刻形貌的分析和计算模型。新催化剂材料的动力学和形态学效应将被检查并纳入模型。这项研究将更好地了解MaCE动力学如何与催化剂颗粒形状相互作用以创建3D纳米结构，最终目标是提供对蚀刻方向的精确控制。在过去的十年里，人们对纳米材料和纳米技术产生了极大的兴趣，这一方面是由于工业界对更低成本、更复杂的设备的渴望，另一方面是由于纳米技术为科学家提供了在接近原子水平上探索自然基本特性的机会。为了实现这些目标，世界各地的研究人员都在努力完善现有技术，并开发新的纳米制造方法；然而，目前还没有一种技术能够以低成本生产高纵横比、光滑壁的复杂2D和3D纳米尺寸特征。目前的纳米制造方法面临两个重要的局限性。首先，如果不是不可能的话，3D几何是很难制造的，需要多个光刻步骤，既昂贵又不能很好地扩展到工业水平的制造要求。其次，随着特征尺寸缩小到纳米领域，在大的深度和高度上精确地保持这些特征变得越来越困难。以经济实惠和高精度生产这些结构的能力对许多现有和新兴技术至关重要，例如用于高频段通信设备的超材料，用于低成本检测癌症和其他疾病的先进生物芯片设备的纳米流体，用于快速，低成本制造的纳米压印光刻等等。该研究旨在发展对MaCE的基本理解，将其作为一种新方法，即使在高纵横比和低成本的情况下，也可以创建具有高特征保真度的2D和3D纳米结构。世界各地的科学家正在寻求使用纳米材料来减少人类活动对环境的影响，而拟议的研究将有助于实现这一目标所需的技术。

The proposed research seeks to understand the fundamental mechanisms involved in catalyst motion in Metal-assisted Chemical Etching of Silicon(MaCE). MaCE is a new, novel method to etch complex 2D and 3D shapes such as subsurface cycloids and 3D spiraling structures while maintaining tight feature resolutions on the order of 1 nm even with aspect ratios 50:1. These capabilities are enabled by the fact that the metal catalyst that defines the etching profile travels into the silicon as the silicon is etched by a galvanic reaction across the catalyst, resulting in etching profile is tightly maintained over the entire etch length along with the ability to etch 3D structures by controlling catalyst motion.While the stoichiometric chemistry of MaCE has been reasonably established, the fundamental kinetics and forces involved in particle motion have remain unknown and unstudied. The proposed research will examine how etchant composition, catalyst shape, catalyst composition and external fields affect the kinetics and forces of MaCE to determine etching rate, resolution, morphology and direction. Also, analytical and computational models of the electric fields, forces, catalyst motion and etching morphology will be developed. The kinetic and morphological effects of new catalyst materials will be examined and incorporated into the models. This research will provide a greater understanding on how the kinetics of MaCE along with the catalyst particleshape interact to create 3D nanostructures with the ultimate goal of providing precise control over etching direction.The considerable interest in nanomaterials and nanotechnology over the last decade is attributed to both the desire by industry for lower cost, more sophisticated devices and the opportunity that nano-technology presents for scientists to explore the fundamental properties of nature at near atomic levels. In pursuit of these goals, researchers around the world have worked to both prefect existing technologies and also develop new nano-fabrication methods; however, no technique exists that is capable of producing complex, 2D and 3D nano-sized features with high aspect ratios, smooth walls, and at low cost. Current nanofabrication methods face two important limitations. First, 3D geometry is difficult if not impossible to fabricate requiring multiple lithography steps that are both expensive and do not scale well to industrial level fabrication requirements. Second, as feature sizes shrink into the nano-domain, it becomes increasingly difficult to accurately maintain those features over large depths and heights. The ability to produce these structures affordably and with high precision is critically important to a number of existing and emerging technologies such as metamaterials for high-band with communication devices, nano-fluidics for advanced bio-on-a-chip devices to detect cancer and other disease at low cost, nano-imprint lithography for rapid, low cost fabrication, and more.The proposed research seeks to develop the fundamental understand of MaCE as a new method to create 2D and 3D nanostructures with high feature fidelity even at high aspect ratios and a low cost. Scientists around the world are looking to use nanomaterials to reduce the environmental impact of human activities and the proposed research will help enable the technology needed to achieve this goal.