2-D row-column CMUT arrays with an open-grid support structure

Fabrication and characterization of 64 + 64 2-D row-column addressed CMUT arrays with 250 μm element pitch and 4.4 MHz center frequency in air incorporating a new design approach is presented. The arrays are comprised of two wafer bonded, structured silicon-on-insulator wafers featuring an open-grid support structure on top of the CMUT plates, omitting the need for through wafer vias. A 5 mask process is used to produce 2-D row-column addressed CMUT arrays with 74 nm vacuum gaps, single crystalline silicon plates with optional lithographically defined mass loads, 120 V pull-in voltage, and high voltage insulation up to 310 V.