A Lithographic Resist-Based Simple Technology for High Yield Microfabrication of Air Bridges

A resist (ma-N 2403 and ZEP 520A7)-based convenient technology to fabricate air bridges on arbitrary substrate is proposed. It involves only two steps of electron-beam lithography. By changing the exposure dose during lithography, the resist can be cross-linked to different extent, and the permanently cross-linked polymer is used for piers. An evaporated 205-nm-thick Ti/Au thin film is used to construct the bridges. Typically, the air bridge is more than 18 μm long, 2 μm high, and 5 μm wide. Due to the accumulated strain in the metal, it naturally forms an arch bridge, rendering no need for critical point drying. The adhesion between the metal and the polymer is considerably strong, even surviving mild sonication. This letter should contribute to a facile technology for manufacturing air bridges for various applications in microelectromechanical systems.