Quan Yuan

Achieving ultrahigh‐quality factors (Q) on high‐coupling piezoelectric substrates remains a significant challenge in surface acoustic wave (SAW) technology. In this work, we designed and fabricated a novel SAW resonator on a 128° YX‐cut lithium niobate substrate utilizing a unique annular interdigital transducer geometry. This closed‐loop design creates a natural acoustic cavity that inherently suppresses diffraction loss and parasitic reflections, achieving efficient energy confinement. Radio frequency characterization of the 39.787 MHz fundamental mode confirmed a record Q factor of 17,466 within a highly compact device footprint, significantly exceeding that of conventional lithium niobate designs. To evaluate the device's stability and potential for sensing applications, we performed comprehensive thermal characterization from 30°C to 150°C. The resonator exhibited a stable temperature sensitivity of −2.425 kHz/°C with near‐perfect linearity and excellent repeatability. These results demonstrate that the proposed annular architecture effectively resolves the traditional trade‐off between electromechanical coupling and Q factor, providing a high‐performance platform for advanced acoustic devices.

To mitigate the substantial degradation of the quality factor (Q factor) in traditional piezoelectric microelectromechanical systems (MEMS) resonators, primarily due to anchor loss and mode competition, this study introduces a coupled dual-beam structure based on aluminum nitride (AlN) for piezoelectric resonators. By jointly optimizing the geometric configuration and material stacking of the coupled dual-beam, and exploiting the mechanical coupling effect in the bending mode, effective suppression of anchor loss and energy localization was achieved. Experimental results demonstrate that the proposed resonator attains a Q factor of 1479.17 at a resonant frequency of 301.74 kHz. The device has a temperature coefficient of frequency (TCF) of -27.67 ppm/°C, exhibiting good frequency-temperature linearity. In terms of the manufacturing process, the critical dimensional error of the structure is less than 1 μm, while maintaining compatibility with CMOS processes, ensuring high-precision fabrication and integration. This study validates the potential of the coupled dual-beam structure in improving the Q factor of MEMS resonators, laying a solid foundation for advancing device miniaturization and multifunctional integration.

Conventional fully covered electrodes in piezoelectric microelectromechanical (MEMS) cantilever resonators lead to uneven electric field distribution and the excitation of parasitic modes. Herein, the top and bottom electrodes are made of molybdenum and symmetrically configured in a comb-shaped layout. The proposed design significantly reduces metal coverage and mass loading, effectively suppresses parasitic modes, and demonstrates high drive efficiency. Finite element method simulations were conducted to optimize the device’s design, followed by the fabrication of the cantilever resonator on a silicon-on-insulator substrate, with aluminum nitride (AlN) selected as the piezoelectric material. Experimental measurements in vacuum reveal that the resonator exhibits a resonant frequency of 5.19 MHz and a quality factor of 6259, which is approximately 3.7 times higher than that of the conventional resonator. These results validate the effectiveness of the proposed electrode optimization strategy and offer valuable insights for the advancement of piezoelectric MEMS resonator technology.

AlN-based piezoelectric MEMS resonators have attracted increasing interest in timing, sensing, and RF front-end applications owing to their outstanding performance. However, the quality factor (Q) and the presence of spurious modes in conventional full-coverage electrodes limit device performance. To address these issues, this article proposes a ring-shaped AlN piezoelectric resonator with a symmetric radial sector electrode design on an SOI substrate. By simulation analysis of electrode-mode interactions, the resonator design was optimized to achieve selective excitation of the desired vibration mode. In addition, a double-beam support structure is employed to reduce anchor loss. Experimental measurements confirm that the sector-electrode resonator exhibits a stronger resonance response and achieves a Q factor up to 1975.46, representing a 40% improvement over conventional designs. A temperature stability experiment shows that the TCF is -29.75 ppm/°C. The results, validated by BVD equivalent circuit fitting, demonstrate that optimized electrode geometry offers an effective and scalable pathway to realizing high performance AlN MEMS resonators for next-generation RF applications.

This paper presents a robust, low-power MEMS temperature control platform featuring a novel hybrid control strategy combining Genetic Algorithm and Particle Swarm Optimization (GA PSO) with Fuzzy PID control. Two heater structures, loop and bent types, are designed and simulated to enhance temperature uniformity, revealing that the bent configuration with an electrode thickness of 500 nm provides superior stability. The key innovation lies in the hybrid GA PSO-Fuzzy PID approach, which autonomously optimizes proportional–integral–derivative (PID) parameters, removing the necessity for manual tuning. This methodology effectively reduces temperature overshoot and accelerates response times, outperforming conventional GA PSO-PID control. Experimental results demonstrate substantial performance improvements, including a faster rise time by 1.98 seconds, reduced peak time by 13.4 seconds, and a shorter settling time by 4.8 seconds. Additionally, the platform shows superior disturbance rejection capabilities, quickly recovering to target temperatures. The straightforward design and fabrication process ensures adaptability across various MEMS heater geometries, underscoring the approach’s potential for advanced thermal management applications in MEMS devices.

This paper focuses on a lithium niobate (LN) surface acoustic wave (SAW) resonator with an annular interdigital transducer (AIDT) structure. The fundamental working principles and structural characteristics of this resonator are analyzed. Due to the closed and regular form of the electrode configuration, parasitic SAW reflections are eliminated, which is expected to significantly enhance the device’s Q factor. Finite element method (FEM) simulations were conducted to optimize the device’s performance. A high-performance LN SAW resonator was successfully microfabricated using micro-nano processing technology. The fabricated device demonstrated a resonant frequency of 22.22 MHz and an impressive Q factor of 12245, which is 2-3 times higher than that of conventional SAW resonators with interdigital electrodes, while its surface area is only one-third of theirs. These results offer significant insights and a valuable reference for the development and application of SAW resonators with annular interdigital electrode structures in future research.

Compared to conventional sensors, resonant-based sensors output frequency signals instead of voltage signals and therefore have greater advantages in terms of accuracy, noise resistance, and miniaturization. However, the resonant frequency is sensitive to temperature variation. The oven controlled MEMS oscillators (OCMOs) have proven to be the most promising candidate for highly accurate oscillators. Therefore, when the OCMO is used for timing and sensing applications, better device temperature stability and performance are expected. However, OCMOs are still in the development stage from laboratory to commercial products, and there are few related reviews about OCMOs. This paper reviews typical results of OCMOs in the past decade with the aim of supporting the development of frequency reference and resonant-based sensors. We emphasized the importance of temperature control for OCMOs. Then, the basic concepts and models of the OCMO are introduced. and the development trend of the OCMO is discussed from three aspects: device structure, sensing mechanism, and heating control systems. Finally, the fabrication process, conclusion and outlook are given.

In this paper, the basic concepts of the equivalent model, vibration modes, and conduction mechanisms of MEMS resonators are described. By reviewing the existing representative results, the performance parameters and key technologies, such as quality factor, frequency accuracy, and temperature stability of MEMS resonators, are summarized. Finally, the development status, existing challenges and future trend of MEMS resonators are summarized. As a typical research field of vibration engineering, MEMS resonators have shown great potential to replace quartz resonators in timing, frequency, and resonant sensor applications. However, because of the limitations of practical applications, there are still many aspects of the MEMS resonators that could be improved. This paper aims to provide scientific and technical support for the improvement of MEMS resonators in timing, frequency, and resonant sensor applications.

Resonance, a natural phenomenon, is a fundamental physical property of any object