Structural properties and frequency response of AlN thin film surface acoustic wave device

An AlN thin film for SAW filter applications was deposited on [100] silicon wafers and sapphire (R-plane) by the reactive magnetron sputtering method. Structural and electrical characteristics of the AlN thin film are presented. The highly oriented [002] plane at various operating conditions was observed by XRD. AFM measurement showed that deposited thin film had a smooth surface. The cross-sectional SEM micrograph showed a well-aligned columnar structure. SAW velocity of the interdigital transducer (IDT)/AlN/Si structure was about 5040 m/s in the center frequency of 126 MHz. Insertion loss was measured to be a relatively low value of 22 dB. SAW velocity of IDT/AlN/sapphire structure was 5960 m/s in the center frequency of 297 MHz, and insertion loss was about 48 dB.