Lithium Niobate SAW devices for Multi-parameter Sensing : Modeling and Simulation Studies Using COMSOL Multiphysics®

R. Srivastava[1], S. Kale[1]
[1]Defence Institute Of Advanced Technology, India
Published in 2019

Surface Acoustic Wave devices are classic examples of Micro Electro Mechanical Systems (MEMS). These devices basically utilize inter-digitated electrodes (IDE) and a piezoelectric layer deposited over a substrate. The input IDT is supplied with alternating voltage and because of this, there exists an alternating polarity between the electrode fingers which cause an inverse piezoelectric phenomena resulting in formation of Surface Waves. These surface waves travel across the delay line and reaches the output IDT and gets transformed to electrical quantity which is then measured. The delay line represents a sensing environment, which is being explored for various parameters.

Through this work we discuss SAW devices fabricated using a non-linear optical material, namely Lithium Niobate. The material used for the electrodes is aluminum. Lithium Niobate is deposited over Silicon substrate using Pulsed Laser Deposition Technique. Aluminum electrodes are etched to yield a SAW device. The thickness of Lithium Niobate layer is taken to be 5000Å and that of Silicon wafer is 0.3mm.

Before fabrication, device was rigorously analyzed using COMSOL Multiphysics® . The model utilizes Structural Mechanics Module involving interface like Piezoelectric devices and Solid Mechanics along with the interface of Electrostatics from AC/DC Module since the model requires an AC excitation at the input to perform study of electrostatics.

Eigen Frequency studies were performed to obtain frequency at which the system will possibly vibrate. Since the elements used in the device have very small dimensions thus it caused a lot of errors, for example “intersecting edges and intersecting face elements”. To eliminate this problem, creation of mesh was done using swept feature of COMSOL Multiphysics® .

  • The device so simulated, will be discussed in detail, in this presentation.