UV Lithography and Molding Fabrication of Ultrathick Micrometallic Structures Using a KMPR Photoresist

By using a novel negative-tone photoresist, KMPR, we have investigated ultraviolet (UV) lithographic microelectroforming fabrication of ultrathick metallic microstructures ( ¿ 400 ¿m). Scanning coating spin speed together with the film thickness and uniformity has been characterized at low spin speed from 1000 to 200 r/min. Based on the film profile characterization, the single-spin lithography conditions for a 400-¿m-thick electroforming mold are optimized by scanning process parameters of UV exposure energy and bake temperature and time. SEM-measured dimensional accuracy and sidewall verticality of the optimized thick KMPR mold are ¿ ¿ 3 ¿m and 90° ±1°, respectively, which are comparable to those of SU8 molds. The SEM analysis of the patterned film and the electroformed structure has shown that the submillimeter-thick KMPR features have ~ 5-10:1 aspect ratio. The sidewall surface roughness of the copper deposition is locally measured to be about ~ 50-100 nm by atomic force microscopy, which is significantly smoother than that resulting from other mechanical machining approaches. This novel photoresist enables the lithographic molding microfabrication process to mass produce plastic and metallic microcomponents for various microelectromechanical systems applications.