A Studv On Lateral Field Excited Thin Film Bulk Acoustic Resonator (FBAR) With Embedded Electrodes

Film bulk acoustic resonators (FBARs) exhibit high resonant frequency, high mass sensitivity, small size and CMOS-compatibility, thus making this technology a promising candidate for chemical and biology sensors. But there are still some shortcomings, such as the existence of spurious modes and the reduction of Q value in liquid environment. We proposed a novel lateral field excited FBAR with embedded electrodes, which has the advantages of pure shear mode resonance and high Q value in liquid environment.The main research contents are:①conducted a mathematical analysis of the lateral field excited FBAR with embedded electrodes;②developed various finite-element models (FEMs) of the lateral field excited FBAR with embedded electrodes and implemented the analysis using ANSYS;③systematically studied the influence of substrate temperature on structural properties and deposition rate of AlN thin film deposited by reactive magnetron sputtering and investigate ultra-violet light assisted reactive RF magnetron sputtering technology for deposition of AlN thin films at room temperature;④prepared a lateral field excited FBAR with embedded electrodes with MEMS technology.The main results of this research are listed as follows:1. We had got a mathematical mode of the lateral field excited FBAR with embedded electrodes, proved that this FBAR worked in pure shear wave mode, refined the formula of the shear mode wave velocity and electromechanical coupling coefficient.2. We investigated the lateral field excited FBAR with embedded electrodes with finite-element models study using ANSYS for the first time. Based on this, we creatively analysis the principle and proposed a formula for of the design of embedded electrodes. This work had applied for and got supported by the "National Natural Science Foundation of China Youth Foud".3. Systematically invstigated the influence of substrate temperature on structural properties and deposition rate of AlN thin film deposition by direct current (DC) or radio frequency (RF) reactive magnetron sputtering. AIN thin film with good C-axis preferred orientation would be prepared under appropriate substrate temperature by both DC and RF reactive magnetron sputtering, but DC performed better at the same condition. AIN thin film with good C-axis preferred orientation can be prepared at room temperature by DC reactive magnetron sputtering with optimal condition. The research had been published in "Journal of ELECTRONIC MATERIALS", which was cited by SCI.4. Proposed and developed a UV-light assisted RF reactive magnetron sputtering method to deposite AIN thin film with controlled crystal orientation at room temperature.(002) oriented columnar AIN crystal can be deposited at high power; while (100) oriented crystal structure can be obtained when the N2/Ar flow ratio is increased to80/40sccm with UV-light assistance at room temperature by RF reactive magnetron sputtering. The research had been published in "Materials Letters", which was cited by SCI.5. We had fabricate a FBAR on a CMOS IC at quite low temperature below350℃cooperate with tsinghua university. The research had been presented on "RF MEMS, Resonators, and Oscillators".6. For the first time, we had successfully prepared a lateral field excited FBAR with electrodes and Bragg reflector, the resonant frequency is1.61GHz.The research of this doctoral dissertation will promote the development of FBAR technology in chemical and biology sensing applications.