Fabrication of circular diaphragm for piezoelectric acoustic devices

This paper describes a fabrication method of a circular diaphragm using boron etching stop method. It is applied to acoustic transducers such as microphones or microspeakers and so on. The sensitivity is expected to be increased with the circular diaphragm through the simulation results to compare with a general rectangular diaphragm. The boron-doped layer which is doped with solid source is sufficient for achieving an etching stop in 20 wt% TMAH, and the thickness is about 7.4 /spl mu/m. The diameter of the circular silicon nitride diaphragm was measured to be 2 mm with 1 /spl mu/m thickness. The fabrication of piezoelectric acoustic devices was completed.