50 nm thick AlN Films for Actuation and Detection of Nanoscale Resonators

We report on the optimization of a multilayer platinum/aluminum nitride (AlN) stack with an AlN active layer thickness of 50 nm for piezoelectric actuation in nanoelectromechanical systems (NEMS). Experiments in reactive sputtering of AlN were used to find optimal parameters for good crystallinity and low residual stress of a four layer film stack, shown in Figure 1. A direct relationship was measured between the AlN seed layer thickness and the x-ray diffraction (XRD) rocking curve’s full width at half maximum (FWHM) of the AlN active layer. However, no influence of seed layer thickness was found in double beam laser interferometric measurements of the clamped longitudinal piezoelectric coefficient d33,f, relating thickness strain from an applied electric field, of the XRD measured four layer film stacks.