Reviewed by Lexie CornerJan 2 2025
Scientists at The Hong Kong University of Science and Technology have developed a novel deep-ultraviolet (UVC) microLED display array for lithography machines, marking a significant advancement in semiconductor technology. The research was published in Nature Photonics.
The electroluminescence (EL) images demonstrate that devices of various sizes perform effectively at operational current densities, even for the smallest 3 µm device. The UVC micro-display can offer exceptional uniformity and significant light output power, enabling the successful implementation of the pattern transfer process. Image Credit: The Hong Kong University of Science and Technology
The UVC microLED developed by the research team provides sufficient light output power density, enabling more efficient and cost-effective maskless photolithography by reducing the time required to expose photoresist films.
The study, conducted in collaboration with the Southern University of Science and Technology and the Suzhou Institute of Nanotechnology of the Chinese Academy of Sciences, was led by Prof. KWOK Hoi-Sing, Founding Director of the State Key Laboratory of Advanced Displays and Optoelectronics Technologies at HKUST.
Lithography machines are crucial for semiconductor manufacturing, as they use short-wavelength ultraviolet light to produce integrated circuit chips with complex layouts. However, conventional mercury lamps and deep UV LED light sources face challenges such as large device size, low resolution, high energy consumption, poor light efficiency, and inadequate optical power density.
To address these limitations, the research team developed a prototype maskless lithography platform and utilized it to fabricate the first microLED device using deep UV microLEDs with maskless exposure. This innovation enhances optical extraction efficiency, heat distribution, and epitaxial stress relief during production.
The team achieved key breakthroughs for the first microLED device, including high power, high light efficiency, high-resolution pattern display, improved screen performance, and fast exposure ability. This deep-UV microLED display chip integrates the ultraviolet light source with the pattern on the mask. It provides sufficient irradiation dose for photoresist exposure in a short time, creating a new path for semiconductor manufacturing.
Hoi-Sing Kwok, Professor and Founding Director, The Hong Kong University of Science and Technology
Kwok explained, “In recent years, the low-cost and high-precision maskless lithography technology of traditional lithography machines has become an R&D hotspot because of its ability to adjust the exposure pattern, provide more diverse customization options, and save the cost of preparing lithography masks. Photoresist-sensitive short-wavelength microLED technology is therefore critical to the independent development of semiconductor equipment.”
Dr. FENG Feng, a postdoctoral research fellow at HKUST’s Department of Electronic and Computer Engineering (ECE), concluded, “Compared with other representative works, our innovation features smaller device size, lower driving voltage, higher external quantum efficiency, higher optical power density, larger array size, and higher display resolution. These key performance enhancements make the study a global leader in all metrics.”
The study has received significant industry recognition, with the 10th International Forum on Wide Bandgap Semiconductors (IFWS) naming it one of the top ten advancements in China's third-generation semiconductor technology in 2024.
Looking ahead, the team aims to improve the performance of AlGaN deep ultraviolet microLEDs, optimize the prototype, and develop 2k to 8k high-resolution deep ultraviolet microLED displays.
The research team includes ECE postdoctoral research fellow Dr. Yibo Liu, Ph.D. graduate Dr. Ke Zhang, and collaborators from partnering institutions. Dr. Feng is the first author; the corresponding author is Prof. Zhaojun Liu, Adjunct Associate Professor in HKUST’s ECE Department and Associate Professor at the Southern University of Science and Technology.
Journal Reference:
Feng, F., et al. (2024) High-power AlGaN deep-ultraviolet micro-light-emitting diode displays for maskless photolithography. Nature Photonics. doi.org/10.1038/s41566-024-01551-7.