Solidly mounted resonator based on aluminum nitride thin film

A piezoelectric thin film sandwiched between two conductors is the basic structure for high frequency bulk acoustic wave devices. For that purpose, AlN thin films deposited by DC reactive sputtering on various electrode materials were investigated. Highly c-axis oriented thin films as thick as 2 /spl mu/m were grown and analyzed. Intrinsic stress values ranging from strong compression to high tension were observed and piezoelectric d/sub 33,f/ coefficients up to 3.9 pm/V were measured. Solidly mounted resonators with a 10-layer acoustic reflector have been fabricated. They exhibited a pronounced resonance peak centered at 2 GHz with a high Q factor and a k/sup 2/ coupling coefficient of 1%. These characteristics are discussed as a function of the processing conditions and the thin film properties.