CAREER: Electrochemical Nanoimprinting of Inorganic Semiconductors: Towards Manufacturing of Three-dimensional Free-Form Optical Devices

该学院早期职业发展（CAREER）资助研究了在关键的电子级无机半导体（如硅，锗和砷化镓）中扩大三维结构生产的方法。二维结构之外的图案化对于设计新颖的基于超材料的红外光学器件至关重要，例如（i）数据中心中的高速光学互连和（ii）用于生物传感和夜视应用的先进成像概念。由于现有的半导体制造工艺不能以所需的分辨率、产量、准确度、均匀性和可重复性来制造三维分层特征，这些设计机会受到阻碍。本计画针对一新兴的奈米压印技术-金属辅助电化学奈米压印（Mac-Imprint），进行整合实验与理论的研究。通过理解Mac-Imprint中化学催化和质量传输的基本原理，我们试图在吞吐量的物理极限下大规模生产跨越四个数量级（即10 nm - 100 µm）的三维分层特征，以实现这些应用。这代表了对高风险和高回报的基本纳米制造问题的追求，否则这些问题对工业来说过于昂贵和危险，同时培训和多样化未来的美国制造业劳动力。此外，该项目旨在通过综合研究和推广活动，提高高中生和大学生对制造工程师在社会中的作用的认识。尽管十年来一直在努力将纳米压印光刻（NIL）的可图案化介质库扩展到聚合物材料之外，但由于基于热的NIL方法的重结晶效应，无机单晶半导体的纳米压印受到限制，削弱其光电性能。为了解决这些挑战，该项目研究了Mac-Imprint，它利用湿化学和催化在室温下在半导体和金属涂层印模的界面处选择性地诱导各向异性蚀刻。通过探索由介孔材料组成的先进印模材料-传统上用于水过滤和净化-寻求促进扩散并增强Mac-Imprint的工艺性能（即分辨率，吞吐量，均匀性）。在基本层面上，我们的目标是了解这类新的金属涂覆的曲折中孔印模材料的有效扩散常数的缩放，其孔径小于50 nm，并将其与Mac-Imprint的工艺性能相关联。当所研究的印模孔隙的长度尺度进入德拜长度范围时，它限制了扩散，并对Mac-Imprint的吞吐量和分辨率施加了物理限制。因此，该项目研究了Mac-Imprint的过程-结构关系，该关系偏离了经典的质量传输模型，并解释了邮票的几何形状及其氧化还原电化学机制的复杂性。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) grant investigates methods of scaling the production of three-dimensional structures in key electronic-grade inorganic semiconductors such as Silicon, Germanium and Gallium Arsenide. Patterning beyond two-dimensional structures is critical to enable the design of novel metamaterial-based infrared optical devices such as (i) high-speed optical interconnects in data centers and (ii) advanced imagining concepts for biosensing and night-vision applications. These design opportunities are hindered due to the inability of existing semiconductor manufacturing processes to fabricate three-dimensional hierarchical features with the required resolution, throughput, accuracy, uniformity and repeatability. In this project, an emerging format of nanoimprinting lithography, metal-assisted electrochemical nanoimprinting (Mac-Imprint) is studied through an integrated experimental and theoretical methodology. By understanding the fundamentals of chemical catalysis and mass transport in Mac-Imprint, it is sought to mass produce three-dimensional hierarchical features spanning four orders of magnitude (i.e. 10 nm – 100 µm) in scale at the physical limits of throughput to enable these applications. This represents the pursuit of high-risk and high-reward fundamental nanomanufacturing problems that otherwise are too costly and risky for industry while training and diversifying the future U.S. manufacturing workforce. Further, this project seeks to increase awareness of the role manufacturing engineers have in society for high-schoolers and undergraduates through integrated research and outreach activities.Despite a decade of efforts to extend nanoimprint lithography (NIL)’s library of patternable media beyond polymeric materials, nanoimprinting of inorganic single-crystalline semiconductors has been restricted due to recrystallization effects of heat-based NIL approaches, curtailing its optoelectronic properties. To resolve these challenges, this project investigates Mac-Imprint which exploits wet-chemistry and catalysis to selectively induce anisotropic etching at the interface of a semiconductor and a metal-coated stamp at room temperature. By exploring advanced stamp materials composed of mesoporous materials - traditionally used in water filtration and purification – it is sought to promote diffusion and enhance the process performance of Mac-Imprint (i.e. resolution, throughput, uniformity). At the fundamental level, the goal is to understand scaling of the effective diffusion constant of this new class of metal-coated tortuous mesoporous stamp materials with sub-50 nm pore sizes and correlated it to the Mac-Imprint’s process performance. As the reserched length scale of the stamp’s pores enters the range of the Debye length, it restricts diffusion and imposes a physical limit to throughput and resolution of Mac-Imprint. Thus, this project examines process-structure relationships of Mac-Imprint that depart from classical mass transport models and account for the complexity of the stamp’s geometry and its redox electrochemistry mechanism.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.