Sensitivity enhancement in diaphragms made by aluminum nitride thin films prepared on polyimide films

Abstract

The authors have investigated a combination of high and low modulus materials in diaphragms for high sensitivity response. High and low modulus materials are aluminum nitride (AlN) thin films and polyimide films, respectively. AlN was sputtered deposited. The AlN films consist of columnar crystal grains and indicate c-axis orientation. The diaphragm indicates a high sensitivity response of 37200pC∕N, although the piezoelectric coefficient d33 of the AlN film is 2.6pC∕N. The sensitivity response is fifty times as high as that of diaphragms consisted of AlN films and superalloy foils.