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.
