Sputtered thin film piezoelectric aluminium nitride as a functional MEMS material and CMOS compatible process integration

A comprehensive study on the complete process module for the fabrication of AlN-based MEMS sensors and actuators is presented. The investigations include the influence of the electrode material, AlN thickness and stress tuning during sputtering on the material parameters, especially the piezoelectric coefficients. It is shown that AlN layers deposited at only 200 °C have good piezoelectric properties. The tuning of residual layer stress has little influence on the piezoelectric properties of AlN. Further two methods of wet chemical etching of AlN are compared. The complete CMOS compatible processing of AlN-based MEMS structures is demonstrated on 200 mm wafers.