High performance AlN-based surface acoustic wave sensors on TiN on (100) Silicon substrate

Fabrication of surface acoustic wave sensors (SAW) based on aluminum nitride (AlN) thin film are reported with improved performance using titanium nitride (TiN) nucleation buffer layer as plate electrode on (100) oriented Silicon (Si) substrate. AlN and TiN thin films are deposited at low temperature by magnetron sputtering and characterized by X-ray diffraction, high resolution transmission electron microscopy, showing good crystalline properties. The insertion loss measured on AlN/Si and AlN/TiN/Si based SAW devices shows clearly that the presence of a TiN nucleation layer improves the acoustic wave device performances. As a final result, a SAW device made on a AlN/TiN membrane by backside etched Si substrate generates symmetrical Lamb wave properties with central frequency at 630 MHz and a phase velocity of 10176 m.s^-1. Operation in the microwave range is possible with appropriate AlN layers.