US Patent 8008105 Methods for fabricating micro-electro-mechanical devices

A method for fabricating a micro-electro-mechanical device (such as a cMUT) is disclosed. The method combines a substrate, a middle spring layer and a top plate using wafer bonding technology or sacrificial technology. A cavity is formed on either the top of the substrate or the bottom of the middle spring layer. A connector is formed on either the top of the middle spring layer or the bottom of the top plate. Upon joining the three layers, the connector defines a transducing space between the top plate and the middle spring layer. The connector is horizontally distanced from the sidewall to define a cantilever anchored at the sidewall. The cantilever and the cavity allow a vertical displacement of the connector, which transports the top wafer in a piston-like motion to change the transducing space. Multiple device elements can be made on the same substrate.