Accessible, large-area, uniform dose photolithography using a moving light source

Photolithography is an essential microfabrication process in which ultraviolet (UV) light is projected through a mask to selectively expose and pattern a light-sensitive photoresist. Conventional photolithography devices are based on a stationary UV lamp and require carefully-designed optics to ensure that a uniform exposure dose is provided across the substrate being patterned. Access to such systems is typically limited to certain labs with domain-specific expertise and sufficient resources. The emergence of LED-based UV technologies has provided improved access to the necessary light sources, but issues with uniformity and limited exposure sizes still remain. In this work, we explore the use of a moving light source (MOLIS) for large-area lithography applications, in which the light source path speed, elevation, and movement pattern can be used to smooth out any spatial variations in source light intensity profiles, and deliver a defined and uniform cumulative UV exposure dose to a photoresist-coated substrate. By repurposing a 3D printer and UV-LED flashlight, we constructed an inexpensive MOLIS platform, simulated and verified the parameters needed to produce a uniform UV dose exposure, and demonstrate this approach for SU-8 microfabrication of features with dimensions relevant to many areas in biomedical engineering. The ready accessibility and inexpensive nature of this approach may be of considerable value to small laboratories interested in occasional and low-throughput prototype microfabrication applications.