UV-LED Lithography for Millimeter-Tall High-Aspect Ratio 3d Structures

This paper introduces a UV-LED lithography system for fabrication of millimeter tall 3-D high-aspect-ratio structures. The proposed system has high intensity collimated light from the light source and a tilt-rotational light propagation at the sample stage to create 3-D light patterns inside a photoresist layer. The lithography system comprises 5-by-5 1.5-W LED array capped with 5° collimated lens, a 4-inch-diameter sample holding plate which can be tilt and rotational, and a microcontroller for the operation of the system. To uniformly distribute the exposed light from the 25 LEDs, the light source was rotated during the exposure process. Two different photosensitive polymers were tested for millimeter tall structures including a widely used negative photoresist, SU-8, and liquid polyurethane, LF55GN. The fabricated millimeter-tall structures include pillars, artistic flowers, microneedle array and a horn structure for an RF antenna.