Cylindrical projection lithography for microcoil structures

This paper reports the development of a novel cylindrical projection lithography (CLitho) device for patterning 3D complex-shaped microstructures along the surface of a cylindrical substrate. To investigate the cylindrical lithographic possibilities of the developed equipment, a solenoidal microcoil structure was lithographed as a patterning sample. As a mask image for CLitho, a mask pattern of multiple lines was used to obtain higher-speed lithography. A photoresist was coated onto the surface of the cylindrical substrate of a metal wire using a conventional spray-coating method. During the lithography, a resist-coated metal wire was simultaneously rotated and moved along the X/θ-direction, and the projected mask pattern was precisely incident upon a resist-coated metal wire. As a result, a solenoidal microcoil structure with coil line width, coil thickness, length, and turn numbers of 12.9 μm, 8.4 μm, 8 mm, and 200 turns, respectively, was clearly lithographed along the surface of a metal wire with only a single rotation. The novelty of this method using CLitho equipment lies in the precise synchronized motion obtained in the X/θ-direction, while keeping the small rotation eccentricity of the wire for the projection exposure of the coil pattern.