Citation
Clement Lorenzo, Marta and Olivares Roza, Jimena and Iborra Grau, Enrique and González Castilla, Sheila and Sangrador García, Jesús and Rimmer, Nick and Rastogi, A. and Ivira, B. and Reinhardt, Alexandre
(2008).
Aluminium Nitride Solidly Mounted BAW Resonators with Iridium Electrodes.
In: "22nd European Frequency and Time Forum (EFTF) 2008", 22/04/2008-25/04/2008, Toulouse, Francia.
Abstract
In this work we investigated the performance of aluminium nitride (AlN)-based solidly mounted resonators (SMR) made with iridium (Ir) bottom electrodes. Ir/AlN/metal stacks were grown on top of insulating Bragg mirrors composed of alternate λ/4 layers of silicon oxi-carbide (SiOC) and silicon nitride (Si3N4).Ir electrodes of various thicknesses were electron-beam evaporated on different adhesion layers, which also acted as seed layers. AlN was deposited by sputtering after conditioning the Ir electrode by a soft-etch with Ar+ ions, which was essential to achieve high quality AlN films. The structure and morphology of the different layers were analysed by x-ray diffraction (XRD) and atomic force microscopy (AFM). The frequency response of the SMRs was assessed by measuring the input scattering parameterS11 with a network analyzer. The experimental results were fitted to the Butterworth-Van Dyke circuital model. The effective electromechanical coupling factor k2eff, and the quality factor Q of the resonators were derived from the experimental data. The influence of the thickness, crystal quality and roughness of the Ir bottom electrodes on the performance of the resonators was investigated.