Reactive Ion Etching of Quartz Substrates Using Three-dimensional Aluminum Masks

Three-dimensional microfabrication is an important process for fabricating microelectromechanical systems (MEMS) and optics. This paper describes reactive ion etching of quartz glass using three-dimensional aluminum masks. Aluminum masks were fabricated using photolithography, anodization, and chemical etching, with the mask shape controlled by anodization and chemical etching conditions. By changing the photoresist mask patterns, quadrangular pyramids and cones were fabricated on quartz substrates using the aluminum masks. Etching characteristics of quartz substrates were developed using CHF3 gas in a planar type plasma reactor. When the process pressure was increased, the etching rate of quartz increased and that of aluminum mask decreased. Based on these results, we increased the selectivity of the quartz/aluminum mask from 10 to 37 by adjusting the pressure. Quadrangular pyramids and cones were fabricated on quartz substrates using this method, which was demonstrated as effective for fabrication of three-dimensional microstructures on quartz substrates.