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

Scandium alloyed aluminum nitride (Al1-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 e(31,f) from -1.28 C/m(2) to -3.01 C/m(2) was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al1-xScxN was found to be tuneable by varying pressure, Ar/N-2 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 Al1-xScxN as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.