Selective electrochemical etching of cantilever-type SOI-MEMS devices

It is possible to achieve selective electrochemical etching between different materials, such as p- and n-type silicon. However, achieving selective electrochemical etching on two different regions of the same p-type silicon material is a problem that has rarely been considered. Herein, a novel selective electrochemical etching technique for cantilever-type silicon-on-insulator (SOI) wafer-based microswitches is proposed. In this study, a p-type handle layer was selectively etched, and a p-type device layer was passivated. This was achieved using a circuit with two voltage sources: voltages of −1.2 and 0 V were applied to the handle and device layers, respectively. It was found that the proposed etching process can effectively prevent the in-use sticking of a cantilever-type switch. This is accomplished by increasing the gap between the device layer and its underlying handle layer and increasing the roughness of these layers. The technique is applicable to the fabrication of various cantilever-type SOI microelectromechanical systems, irrespective of the resistivity of the SOI wafer.