Fabrication of Suspending GAN Microstructures With Combinations of Anisotropic and Isotropic Dry Etching Techniques

A method for fabricating gallium nitride (GaN) based microelectromechanical (MEM) devices on silicon substrate was demonstrated. Various suspended GaN microstructures have been fabricated using ICP (Inductive coupled plasma)-based sacrificial etching of the underlying silicon with combination of both anisotropic and isotropic etching techniques, so that deeply released freestanding microstructures with minimized lateral undercut can be achieved. Cl₂-based ICP-RIE (Reactive ion etching) dry etching technique is employed to pattern gallium nitride. The experimental results show that freestanding GaN microstructures with large air gap of high depth-to-width ratio can be realized by employing such two-step dry releasing technique. Fabrication results have been characterized by scanning electron microscope (SEM).