Study Of Thin Film Bulk Acoustic Resonator (fbar) Technology

Thin film bulk acoustic resonator (FBAR) is a breakthrough technology for RF filter. It can replace conventional SAW filter because it provides several prominent advantages such as small size, high Q, high power handling capability, high operating frequency, good temperature stability, and the possibility of being integrated into RFIC (Radio Frequency Integrated Circuits).Deposition of high-quality A1N thin film is a key to success in FBAR manufacture. Due to the constrain of research conditions, we choose four main parts to study, which include the modeling of FBAR, deposition of AIN thin film, measurement of permittivity of AIN thin film, and the design and implementation of FBAR devices. The main results of this dissertation are listed as follows:1. An equivalent circuit model which is suitable for many kinds of FBAR, such as air-gap, back etched, solid mounted, and overmode type was presented. An electromagnetic model which is suitable for commercial 3D electromagnetic soft was presented. Based on these models, we built up the simulation library of ADS and implemented the acoustic-electromagnetic co-simulation with HFSS. The models were validated by comparison with experimental data.2. Based on the reactive sputtering processes modeling, we provided a new method to get high deposition rate as well as high c-axis oriented for AIN thin film. The proposed method uses the flow of N₂ as control quantity, and the cathode voltage as location quantity. The targets work at transition region between metallic state and poisoned state, and there are no hystereses during the processes. Finally, at 500 W RF power, the deposition rate achieves 2.3 μ m per hour.3. A method and apparatus for complex permittivity measurement of dielectric thin film was proposed. It is based on cavity perturbation theory, and dielectric thin film is used as perturbation quantity. By comparison the frequencies and Q values before and after the perturbation, we can get the permittivity of dielectric thin film. The experimental data show that the precision of this method for A1N thin film is less than 5%. The method and apparatus were applied for patent.4. Designed an unbalanced and balanced Rx filter for WCDMA zero-IF receiver, respectively. The topologies of filters are composed of ladder and lattice topology. The responses of filters both have steep roll-off and deep stop band rejection, and the balanced Rx filter also has good common mode rejection.5. Designed and manufactured the prototype of overmode FBAR on double-side polished (111) silicon wafer. The frequency distribution measured by Vector Network Analyzer (VNA) is similar to that simulated by ADS.We have designed the processes flow and mask for the back-etched type FBAR, butwe did not manufacture it due to the research conditions. It is the biggest shortage of this dissertation.