Optimization of 3D SU-8 microstructures using mask-less lithography and ultraviolet exposure

• Main Author: Zhu, Junlei
• Other Authors: Lee Seok Woo
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Chemistry; Engineering; Physics; Maskless lithography; UV exposure; SU-8
• Online Access: https://hdl.handle.net/10356/179410
• Institution: Nanyang Technological University

Maskless lithography has a broad prospect in fabricating 3D microstructures by negative photoresist SU-8, which is popular in MEMS and microfluidics application. Thus, in this dissertation project, I study the optimal UV exposure condition for the DMD-based maskless lithography and build some 3D microstructures by SU-8 photoresist. For SU-8 3050 under 10x Lens, the optimal results are obtained at 60%intensity with 300s exposure time. For SU-8 3010 under 10x Lens, the optimal results are obtained at 50% intensity with 200s exposure time or 60% intensity with 300s exposure time. For SU-8 3050 under 20x Lens, the optimal results are obtained at 70% intensity with 100s exposure time. For SU-8 3010 under 20x Lens, the optimal results are obtained at 40% intensity with 400s exposure time. The 3D SU-8 microstructures can be fabricated by multi-exposure or shallow exposure methods. The former one is suitable for stacked patterns and the other one is suitable for bridge structures. A micromixer and several micro bridges are fabricated and evaluated by SEM.