Optimization of PZT-Based Radio-Frequency Filters

Analytical solutions are presented for the wave equation for the electrode-piezoelectric-electrode sandwich structure in film bulk acoustic resonators (FBAR). The impedance for lead-zirconate-titanate (PZT)-based FBAR was derived using the proper boundary conditions and material parameters. A method is presented to adjust the resonant frequency based on the process and material properties. Ferroelectric-based radio-frequency filters were designed using FBARs. An accurate result is given for the filter impedance which can be used for other piezoelectric devices.     

Surface Micromachining of Bulk Acoustic Wave Filters

The most common typical bulk acoustic wave (BAW) filters are fabricated using bulk micromachining technology, but they have several disadvantages. This paper describes a new structure for front end passband BAW filters manufactured using surface micromachining. Porous silicon is used as a thick sacrificial layer. The structure reduces the influence of the support film on the filter to improve the VLSI compatibility as well as the filter quality. The cross-talk between resonators with different frequencies can be dramatically reduced by using resonators with a self-supporting structure.