Progress in Materials Used for Solidly Mounted Film Bulk Acoustic Resonators

Solidly mounted film bulk acoustic resonator(SMR-FBAR) is a breakthrough technology being developed recently in the field of electronics industry and has many excellent features,such as operation frequency of above 2 GHz, ultra-high Q factor and durable mechanical property,etc.The unique features of the SMR-FBAR make it not only be a hot spot in labs,but also attractive in particular applications.For instance,SMR-FBAR can be used to create the essential frequency shaping elements found in the third generation of wireless communication systems,including filters, duplexers,and oscillators.Materials are the key element in devices and their quality plays a critical role in determining the resonance characteristics of these acoustic resonators.In this paper,with the clue of the structure of device,the recent developments of materials used for solidly mounted film bulk acoustic resonators are reviewed,including piezoelectric films(AlN,ZnO,etc),high/low acoustic impedance materials and electrode films.The relationship between material properties and device performance is also discussed.Finally,the potential development direction on the investigation of materials used for solidly mounted film bulk acoustic resonators is prospected.