Finite Element Modeling and Analysis of Surface Acoustic Wave Devices in CMOS Technology

Finite element modeling (FEM) and performance analysis of surface acoustic wave (SAW) devices that are developed in complementary metal-oxide-semiconductor (CMOS) technology is presented. A detailed 3-D model with 18 CMOS layers and a structured FE analysis methodology are laid out to extract the acoustic behavior of the substrate and the piezoelectric material of interest, ZnO. The model represents the 0.5- μm AMIS three-metal, two-poly process that is used to fabricate CMOS-SAW devices. A three-step analysis that encompasses modal, harmonic, and transient simulations is detailed. Experimental characterization results for the fabricated CMOS-SAW devices with operating frequency of 322.7 MHz show close agreement with the FE simulations with 0.8% and 17% deviations for operation frequency and 3-dB bandwidth, respectively. FEM results also show -6% deviations for maximum rejection bandwidth when compared to the SAW equivalent-circuit-based crossed-field model. Displacement, stress, and strain maps for wave propagation, induced voltage distribution, and phase responses are also presented. The results demonstrate that commercial FEM toolsets can provide valuable insight into understanding acoustoelectric interactions and wave characteristics. Moreover, they can readily be used for accurate design parameter extraction and reliable simulation of SAW device performance in general.