Research of micro area piezoelectric properties of AlN films and fabrication of high frequency SAW devices

Aluminum nitride (AlN) thin films were optimized on Pt/Ti/SiO2/Si (100) substrates by magnetron sputtering at different substrate temperatures (room temperature, 400 °C, 500 °C, and 600 °C). The analysis of X-ray diffraction (XRD) and atomic force microscopy (AFM) indicated that the optimal deposition temperature for AlN films with high (002) orientation, smallest value of rocking curve FWHM and superior grain distribution is 500 °C. Micro area piezoresponse force microscopy (PFM) results show that AlN samples deposited under 500 °C have the highest relative piezoelectric coefficient (d⁎33(max) = 0.79) and uniform piezoelectric performance. Moreover, interdigital transducers (IDT) of submicron scale (finger width 300 nm) were designed and fabricated by electron beam lithography (EBL) and lift-off process. Finally, the Pt/AlN/Pt two-port SAW device cell was constructed, with a device frequency up to 4.47 GHz, and an acoustic velocity of deposited AlN of approximately 5300 m/s. [Display omitted] •The microstructure of AlN films is influenced by the substrate temperature.•The high (002) orientation AlN films have uniform piezoelectric performance.•The high frequency SAW device (f0 = 4.47 GHz) was constructed based on optimal AlN films.