Digital Electrostatic Acoustic Transducer Array

In this paper we present the fabrication and characterization of an array of electrostatic acoustic transducers. The array is micromachined on a silicon wafer using standard micro-machining techniques. Each array contains 2(n) electrostatic transducer membranes, where "n" is the bit number. Every element of the array has a hexagonal membrane shape structure, which is separated from the substrate by 3 mu m air gap. The membrane is made out 5 mu m thick polyimide layer that has a bottom gold electrode on the substrate and a gold top electrode on top of the membrane (250nm). The wafer layout design was diced in nine chips with different array configurations, with variation of the membrane dimensions. The device was tested with 90 V giving and sound output level as high as 35dB, while actuating all the elements at the same time.