MEMS Pirani gauges achieve high-precision measurements of air pressure through multilayer thin-film structures. However, the thin-film structure makes the device vulnerable to thermal stresses during operation due to its insufficient mechanical toughness and limited deformability characteristics. In order to deeply explore the influence of thermal stress on the performance of thin-film devices, this study utilized COMSOL Multiphysics to conduct finite element analysis on MEMS Pirani gauges with two distinct heating mechanisms. The impact of thermal stress on the MEMS Pirani gauge was systematically evaluated by integrating the coupling effects of thermal, mechanical, and electrical multiphysics fields. The numerical simulation outcomes revealed the influence of thermal stress on the sensitivity, stability, and measurement accuracy of the Pirani gauge under varying thermal conditions. It was demonstrated that persistent thermal stress can lead to the degradation of thin-film material properties and electrical characteristic drift, thereby affecting the reliability of the Pirani gauge. The findings provided by the finite element simulation in this study offer crucial insights for the optimal design and risk mitigation strategies of MEMS Pirani gauges. © Published under licence by IOP Publishing Ltd.

This study focusses on heat-generating thermistors in microelectromechanical systems (MEMS) flow sensors and explores their heat-generating characteristics in sand and dust polluted environments. A mathematical model was developed and a corresponding simulation model was constructed to assess the joint effect of dust deposition thickness and external input voltage on the heat generation temperature of the thermistor. The study reveals a significant inhibitory effect of dust particles on the heat transfer efficiency. Controlling for other variables, we established quantitative relationships between thermistor temperature and dust deposition thickness and input voltage. © Published under licence by IOP Publishing Ltd.

With the advancement of semiconductor manufacturing technology, thin film structures were widely used in MEMS devices. These films played critical roles in providing support, reinforcement, and insulation in MEMS devices. However, due to their microscopic dimensions, the sensitivity of their parameters and performance to thermal stress increased significantly. In this study, a Pirani gauge sample with a multilayer thin film structure was designed and fabricated. Based on this sample, finite element modeling analysis and thermal stress experiments were conducted. The finite element modeling analysis employed a combination of steady-state and transient methods to simulate the deformation and stress distribution of the device at room temperature (25 °C), low temperature (-55 °C), and high temperature (125 °C). The thermal stress test involved placing the sample in a temperature cycling chamber for temperature cycling tests. After the tests, the resonant frequency and surface deformation of the device were measured to quantitatively evaluate the impact of thermal stress on the deformation and resonant frequency parameters of the device. After the experiments, it was found that the clamped-end beams made of Pt were a stress concentration area. Additionally, the repetitive thermal load caused the cantilever beam to move cyclically in the Z direction. This movement altered the deformation of the film and the resonant frequency. The suspended film exhibited concavity, and the overall trend of the resonant frequency was downward. Over time, this could even lead to the fracture of the clamped-end beams. The variation of mechanical parameters derived from finite element simulations and experiments provided an important reference value for device design improvement and played a crucial role in enhancing the reliability of thin film devices.

The effect of sand and dust pollution on the sensitive structures of flow sensors in microelectromechanical systems (MEMS) is a hot issue in current MEMS reliability research. However, previous studies on sand and dust contamination have only searched for sensor accuracy degradation due to heat conduction in sand and dust cover and have yet to search for other failure-inducing factors. This paper aims to discover the other inducing factors for the accuracy failure of MEMS flow sensors under sand and dust pollution by using a combined model simulation and sample test method. The accuracy of a flow sensor is mainly reflected by the size of its thermistor, so in this study, the output value of the thermistor value was chosen as an electrical characterization parameter to verify the change in the sensor's accuracy side by side. The results show that after excluding the influence of heat conduction, when sand particles fall on the device, the mutual friction between the sand particles will produce an electrostatic current; through the principle of electrostatic dissipation into the thermistor, the principle of measurement leads to the resistance value becoming smaller, and when the sand dust is stationary for some time, the resistance value returns to the expected level. This finding provides theoretical guidance for finding failure-inducing factors in MEMS failure modes.

Exploring interfacial thermal transport of a heterojunction interface is crucial to achieving advanced thermal management for gallium nitride-based high electron mobility transistor devices. The current research primarily focuses on material enhancements and microstructure design at the interfaces of epitaxial layers, buffer layers, and substrates, such as the GaN/SiC interface and GaN/AlN interface. Yet, the influence of different concentrations of Al/Ga atoms and interface roughness on the interfacial thermal conductance (ITC) of AlGaN/GaN interface, the closest interface to the hot spot, is still poorly understood. Herein, we focus on the rough AlGaN/GaN interface and evaluate the changes in ITC under different Al-Ga atomic concentrations and interface roughness using atomistic simulations. When the interface is completely smooth and AlGaN and GaN are arranged according to common polarization characteristic structures, the ITC gradually increases as the proportion of Al atoms decreases. When the proportion of Al atoms is reduced to 20%-30%, the impact of the interface structure on heat transfer is almost negligible. For interface models with different roughness levels, as the interface roughness increases, the ITC drops from 735.09 MW m−2K−1 (smooth interface) to 469.47 MW m−2K−1 by 36.13%. The decrease in ITC is attributed to phonon localization induced by rough interfaces. The phonon modes at the interface are significantly different from those in bulk materials. The degree of phonon localization is most pronounced in the frequency range that contributes significantly to heat flux. This work provides valuable physical insights into understanding the thermal transfer behaviors across the rough AlGaN/GaN interfaces. © 2024 Author(s).

Microfluidic heat sinks are regarded as an efficient cooling solution in micro-electronic systems. However, as the hydraulic diameter of the microfluidic heat sinks shrinks, the blockage problem may occur due to the particles caused by cooling components’ abrasion, which limits the application in long-term operation. This paper proposes an unconstrained microfluidic heat sink (UCMFHS) with high anti-blockage capacity for multiple hotspot systems, which aims to solve the blockage problem. The position and shape of the micro pin fins in UCMFHS are optimized by the CFD model. According to the test requirements of anti-blockage capacity and cooling performance, the test platform is built, which adopts the thermal test chips as heat source array. The results show that when the coolant particle concentration is 0.5%, the pressure drop variation is less than 0.3 kPa in UCMFHS, which is 99.43% lower than the control sample. The average temperature and temperature non-uniformity coefficient of 16 hotspots under the condition of 1200 W/cm2 and 125 mL per minute are 141.1 ℃ and 0.049, respectively. Therefore, the UCMFHS has both anti-blockage capacity and cooling capacity and is considered to have a high application prospect in long-term multi-hotspot cooling. © 2024 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This is an open access article distributed under the CC BY-NC-ND 4.0 terms and conditions.

The effect of organic contamination on the sensitive comb structure of accelerometers in microelectromechanical systems (MEMS) is hardly involved in the original MEMS reliability study, because the existing technology can guarantee chip packaging in the absence of contamination, but with the advancement and popularity of multi-chip packaging technology, some chip devices may have organic substances volatilised and have an effect on the strength of the comb structure of accelerometer devices, thus affecting the service life of the devices. However, with the progress and popularity of multi-chip packaging technology, some of the chip devices may have volatilisation of organic substances, which may affect the strength of the acceleration sensor comb, and thus the service life of the device. In this paper, the theoretical derivation and experimental verification method to complete the study, and in the organic pollution test, organic substances will mainly have an impact on the strength of the comb structure of the acceleration sensor, so this paper focuses on the comb structure before and after the organic pollution of the strength of the change. The results of the experimental study show that the strength of the comb structure of the MEMS device decreases to a certain extent after the contamination compared with that before the contamination. This research result provides a theoretical basis for finding the failure inducing factors in the MEMS failure mode and predicting the device life. © 2024 IEEE.

This letter reports a wide band linearly polarized(LP) and orbital angular momentum (OAM) mode reconfigurable magneto-electric (ME) dipole antenna array. A switchable microstrip balanced feed structure (MBFS), which can provide a stable phase difference of 180-degree in the whole operating frequency band, is employed in the design of ME dipole element. By using two orthogonal MBFS, two high-isolation LP modes with switchable 180-degree phase shifting characteristics can be generated, enabling the reconstruction of LP modes through polarization synthesis. By manipulating the states of the reconfigurable feed network and the four ME dipole elements, the polarization can be altered among two orthogonal LP states and the OAM mode can be reconfigured between l=-1,0,and+1.The measurement results indicate that the proposed ME dipole array exhibits good reflection coefficient in the frequency range of 3.0-4.0 GHz (|S11| IEEE

This paper presents a new method for wafer-level packaging of MEMS silicon-on-insulator (SOI) sensors and actuators working in the situation of over-loading. The developed process starts with backside deep reactive ion etching (DRIE) of the substrate to define the support structures as down stop blocks. This is followed by hydrofluoric acid etching to remove excessive SiO2 layer underneath the structural area to free the movable device parts. Then, another step of DRIE was applied on the device layer to form the device features. As the area of support structures are much smaller than proof mass, no stiction was observed. Finally, a glass wafer was used to encapsulate the switch using an anodic bonding technique to form a up stop block. In the work described here, the process is demonstrated for micromachining of an optical switch surviving from the high-impact overload environment at 20,000 g with pulse-width 120 μs. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

本课题研究的主要内容包括:1高低温及不同真空度下芯片及封装力学特性原位测试技术;2芯片及封装热学特性原位测试技术;3微纳传感结构力—电耦合特性原位测试技术，实现对微观力—电参数的同步提取。4片上表征结构设计及测试技术，针对微器件材料、结构的失配所引起的微结构模态分裂、应力等问题，设计用于表征材料、结构、工艺特性的“在片试验机”,实现对结构应力及封装残余应力或形变的放大及特性参数的测试提取。The main contents of this research project include:1in-situ testing technology of mechanical properties of chips and packages under high and low temperatures and different vacuum degrees;2In-situ testing technology for thermal characteristics of chips and packages;3In-situ testing technology of mechanical-electrical coupling characteristics of micro-nano sensing structures to realize the synchronous extraction of micro-mechanical-electrical parameters.4On-chip characterization structure design and testing technology,aiming at the problems of microstructure modal splitting and stress caused by the mismatch of microdevice materials and structures,a"on-chip testing machine"is designed to characterize the characteristics of materials,structures and processes,so as to realize the amplification of structural stress and packaging residual stress or deformation and the test and extraction of characteristic parameters.