Flexible piezoelectric cantilevers fabricated on polyimide substrate

In this work we present for the first time the fabrication and the characterization of flexible micro cantilevers based on Aluminum Nitride (AlN) as piezoelectric active layer and polyimide as elastic substrate. The AlN thin film, embedded into two layers of Molybdenum (Mo), is grown by sputtering deposition and presents highly c-axis oriented hexagonal crystal structure. The flexible structures are successfully realized by a two masks process, exploiting a silicon support to perform device key fabrication steps together with optimized processes for peeling off and patterning of the flexible layer. The realized flexible cantilevers present a bending downwards because of the residual compressive stress of the Mo/AlN/Mo multilayer on polyimide. The mechanical response of the realized flexible cantilevers has been investigated by piezoresponse measurements and the experimentally obtained first resonance frequency resulted to be around 15 kHz. This value has been compared with simulations of the structures performed by finite element method.