Fully-Differential TPoS Resonators Based on Dual Interdigital Electrodes for Feedthrough Suppression

Abstract

As one of the core components of MEMS (i.e., micro-electro-mechanical systems), thin-film piezoelectric-on-silicon (TPoS) resonators experienced a blooming development in the past decades due to unique features such as a remarkable capability of integration for attractive applications of system-on-chip integrated timing references. However, the parasitic capacitive feedthrough poses a great challenge to electrical detection of resonance in a microscale silicon-based mechanical resonator. Herein, a fully-differential configuration of a TPoS MEMS resonator based on a novel structural design of dual interdigital electrodes is proposed to eliminate the negative effect of feedthrough. The fundamental principle of feedthrough suppression was comprehensively investigated by using FEA (i.e., finite-element analysis) modeling and electrical measurements of fabricated devices. It was shown that with the help of fully-differential configuration, the key parameter of SBR (i.e., signal-to-background ratio) was significantly enhanced by greatly suppressing the in-phase signal. The S-parameter measurement results further verified the effectiveness of this novel feedthrough suppression strategy, and the insertion loss and SBR of proposed TPoS resonators were improved to 4.27 dB and 42.47 dB, respectively.

Modeling the Piezoelectric Cantilever Resonator with Different Width Layers

“…Back to the proposed model, let the applied voltage be the drive voltage, that is 0.2 V. Substituting the geometry and material parameters to (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), the static tip displacement is 1.88 nm, which is larger than the measured result. The reason is that there is a feedthrough capacitor in the resonator [32], which will affect the output current. On the other hand, the nonideal factors exist in the PCB circuit, such as parasitic parameters of electrical elements.…”

Replicating Spectral Baseline for Unambiguous Frequency Locking in Resonant Sensors

“…Therefore, this work aims to optimize the spectral response of the sensor by de-embedding the parasitic signal from the measured signal. Several techniques have been employed to address this parasitic feedthrough effect (FE), including: a phase-controlled oscillation technique for operating microresonators beyond the nonlinear regime with on-chip FE de-embedding [15], the application of a unique design of thin-film piezoelectric-on-silicon (TPoS) MEMS resonator with a fully differential configuration to eliminate parasitic feedthrough effects [16], and the design and performance analysis of a PLL charge-pump with very low feedthrough characteristics [17]. These proposed methods highlight the high level of complexity in the technical approaches and analyses required to tackle feedthrough issues, emphasizing the importance of careful design innovation and control techniques to enhance the performance and operational stability of microresonators and related circuits.…”

“…The impact of these parasitic signals on the measured sensor output can then be estimated and adjusted using this replica. Compared to the prior method [16,18,19], the current approach essentially helps to isolate the genuine signal of interest from the unwanted effects of parasitic variables, resulting in more practical, precise, and dependable measurement (or sensing) performance without the need for modifications to the resonator device used.…”