Fabrication of SAW Devices with Dual Mode Frequency Response Using AlN and ZnO Thin Films

In this study, surface acoustic wave (SAW) devices with dual mode frequency response are fabricated on Si
₃
N
₄
/Si substrate using double-layered piezoelectric thin films. Aluminum nitride (AlN) and zinc oxide (ZnO) are chosen as the piezoelectric thin films because the distinguished piezoelectricity of acoustic wave velocity and electromechanical coupling coefficient. The interdigital transducer electrodes (IDTs) of aluminum (Al) were then fabricated onto the piezoelectric layers by using the sputtering technology combined with photolithography to form the IDT/ZnO/AlN/Si
₃
N
₄
/Si SAW devices. For optimizing the characteristics of resonator and filter applications, the deposition conditions of AlN and ZnO thin films have been investigated. The SAW device shows the resonant frequency of 146.3 MHz (Rayleigh mode) and 265.7 MHz (Sezawa mode). The insertion loss Rayleigh mode and Sezawa mode are -14.2 dB and -17.4 dB, respectively.