DESIGN AND SIMULATION OF FILM BULK ACOUSTIC RESONATOR

Abstract

Number of applications have emerged using FBAR like mass detector, gas sensor, humidity sensor, UV sensor, DNA and protein detector and many more, which motivates the researchers to work further to make most of it. Design and simulation of FBAR is done for the variation in number of parameter and there effects on FBAR. The bulk etching design is selected for the simulation and the 5 different combinations of electrodes are simulated for the parameters like quality factor, coupling coefficient, resonant frequency, impedance response and figure of merit (FOM). In this thesis the analytical results are identified for the same configuration of the electrodes by using the one dimension (Z-axis) analytical approach by using the simple piezoelectric derivations. The losses across the FBAR are identified. Also, methods of suppressing the spurious modes are discussed and simulated. The simulation is carried out for the anchor losses effect on the quality factor and resonant frequency. The effect of damping factor variation is simulated and shown the inverse relationship in between them. The methods for suppression of spurious modes are simulated in the Comsol as well as CoventorWare. The results suggest an effective suppression. The effect of change in the area is simulated to identify the effect on the impedance which helps to connect the filter in the communication line with the maximum power transfer condition satisfied. Centre mass loading technique is simulated and the sensitivity is measure for the mass change. This technique is used in many applications like detection of the RDX particles in the environment. Also, the simulation is carried out in Comsol software to find the change in sensitivity for the shifting of mass from centre position to the corner position. The sensitivity comes out to be decreased as the mass shifted towards the corner. Butterworth Van-Dyke equivalent circuit parameters are also used to find out the resonant frequency obtained from the simulation by using the different equations. AlN is used as the choice for the piezoelectric material because of its superior acoustic properties from the other materials. Different types of electrodes are used viz. Aluminum, Platinum, Tungsten, Molybdenum and combination of electrodes. AlN layer is deposited by the sputtering technique over the Aluminum layer. Silicon is taken as the substrate over which the cleaning and photolithography is done to form the different patterns expose. Sputtered AlN layer is characterized by using FTIR, SEM, and EDS etc.