Sputter deposition of piezoelectric AlN and AlScN films for ultrasonic and energy harvesting applications

This paper reports on the deposition and characterization of highly piezoelectric aluminium nitride (AlN) and aluminium scandium nitride (AlXSc1-XN) thin films. Characterization methods include XRD, SEM, pulse echo and piezoemeter measurements. The deposition of highly piezoelectric AlN films was achieved with deposition rates up to 200 nm/min on a coating diameter of 200 mm. Additionally, the energy harvesting properties of AlN due to ambient mechanical vibrations are demonstrated with a basic cantilever structure of Si with AlN on top. This basic and not optimized design showed a power generation ability of several 10 µW to several 100 µW for an excitation vibration with displacement amplitudes from 2.5 µm to 7.5 µm peak-to-peak and frequencies of around 600 Hz.