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

• Published in: Journal of microelectromechanical systems Vol. 19; no. 3; pp. 683 - 689
• Main Authors: Young-Min Shin, Gamzina, Diana, Barnett, Larry R, Yaghmaie, Frank, Baig, Anisullah, Luhmann, Neville C
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Atomic force microscopy; Atomic measurements; Coatings; Electroforming; Electronics; Exact sciences and technology; Fabrication; Force measurement; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; KMPR; Lithography; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Microelectromechanical systems; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Microstructure; molding; Molding (process); Molds; Photoresists; Physics; Precision engineering, watch making; Resists; Scanning; Scanning electron microscopy; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Studies; Temperature; ultraviolet (UV); Verticality; ultraviolet (UV); Atomic force microscopy; Scanning electron microscopy; Molding; Electroforming; Low speed; Precision engineering; Roughness; KMPR; lithography; Aspect ratio; Layer thickness; Operating conditions; Ultraviolet radiation; UV lithography; Spin-on coatings; Microelectromechanical device; Mold; Nanotechnology; Photoresist; Production process
• ISSN: 1057-7157; 1941-0158; 1941-0158
• DOI: 10.1109/JMEMS.2010.2045880

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.