FABRICATION OF SINGLE-CHIP POLYSILICON CONDENSER STRUCTURES FOR MICROPHONE APPLICATIONS

This paper describes a single-chip microphone structure and its fabrication using polysilicon for both condenser electrodes. The fabrication technology is IC-compatible with KOH-etching on one wafer surface only to form the membrane in a last step. The membrane dimensions range from 100 mu m by 100 mu m to 500 mu m by 500 mu m. The membrane thickness and the air gap is 1.5 mu m while the thickness of the backplate is 3.5 mu m. For increased mechanical sensitivity slotted membranes were also fabricated. The static deflection behaviour due to electrostatic forces was simulated and measured.