Fabrication of five-layer three-dimensional miniature SU-8 axial fans using ultraviolet lithography

Abstract

As miniaturization technologies have improved for the past few decades, electronic devices are becoming smaller and the technology needed to fabricate complex three-dimensional (3D) microstructures becomes important. Photolithography is a relatively simple and low-cost method. However, photolithography is, in general, a fabrication method for planar two-dimensional microstructures. In this study, a technique using photolithography is developed to fabricate three-dimensional blades for axial microfan applications. Fabrication of a five-layer SU-8 microstructure for a miniature axial fan of 5 mm diameter using ultraviolet (UV) lithography is presented. Each SU-8 layer was fabricated with a small shift relative to the previous layer. Hence, 3D SU-8 blades with oblique sections have been successfully fabricated using this relatively simple UV lithography. A multiple resist coating and exposure with a single development stage was employed. It was observed that the exposure time for the second to fifth layers was reduced by a factor of 0.7 as compared to that needed for the first layer. A relatively efficient method for the fabrication of multilayer oblique walls was developed. It is probably the first time that UV lithography is used for creating 3D sloping microstructures.