Analysis and design of IDT/ZnO/Si resonator filter using coupling-of –modes theory

In our work, a monolithic integration of RF filter SAW, on a semiconductor substrate such us Si or GaAs is highly desirable to miniaturize the outer dimensions and introduce the new functionalities of the cellular phones. But, direct monolithic integration of SAW filters is impossible with Si which is non piezoelectric and difficult with GaAs which is weakly piezoelectric. One alternative is the deposition of a piezoelectric film on the semiconductor substrate. We propose a modified coupling of modes (COM) approach, which can be used in the practical design of a layered ZnO/Si surface acoustic wave filter. We present an analysis and realisation of a ladder-type SAW filter using six resonators. The filter will be developed on a structure with three layers of a ZnO film and aluminium (Al) electrodes on a silicon (Si) substrate in the 930-960MHz frequency band range. This is a dispersive SAW layered filter, and some of the COM parameters become frequency dependent due to the phase velocity dispersion. The frequency response of the 3 step (6 resonators) ladder type IDT/ZnO/Si SAW filter is analysed and compared with the experimental results. This transfer function confirms that it is possible to integrate on Si substrate the filters use for GSM and DECT systems.