Solidly Mounted Bulk Acoustic Wave Filters

ABSTRACTSelective RF filters based on solidly mounted thin film bulk acoustic wave resonator filters (SMR filters) are of great interest for mobile and wireless applications in the GHz frequency range. They are small in size, robust and can be integrated on silicon. The SMR configuration comprises a textured piezoelectric layer of AlN or ZnO sandwiched between two electrodes, and an acoustic reflector, which confines the acoustic energy in the resonator region. The bulk acoustic wave (BAW) resonators are exited in the thickness extensional mode. In these paper examples of BAW resonators and filters for the frequency range between 1 and 8 GHz are shown. It will become clear that precise control of AlN film growth is very important. Modelling the resonator performance using a 1-dimensional electro acoustical model allows the extraction of important thin film parameters and thus simulation of the filter performance. Limitations of the 1-D model are discussed.