Stress controlled pulsed direct current co-sputtered Al1-xScxN as piezoelectric phase for micromechanical sensor applications

Scandium alloyed aluminum nitride (Al 1−xScxN) thin films were fabricated by reactive pulsed direct current co-sputtering of separate scandium and aluminum targets with x < 0.37. A significant improvement of the clamped transversal piezoelectric response to strain e31,f from −1.28 C/m2 to −3.01 C/m2 was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al 1−xScxN was found to be tuneable by varying pressure, Ar/N2 ratio, and Sc content. The thus resulting enhancement of the expectable signal to noise ratio by a factor of 2.1 and the ability to control built-in stress make the integration of Al 1−xScxN as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive.