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Hydraulic technology with smaller sizes and higher reliability trends, including fault prediction and intelligent control, requires high-performance temperature and pressure-integrated sensors. Current designs rely on planar wafer- or chip-level integration, which is limited by pressure range, chip size, and low reliability. We propose a small-size temperature/high-pressure integrated sensor via the flip-chip technique. The pressure and temperature units are arranged vertically, and the sensing signals of the two units are integrated into one plane through silicon vias and gold–gold bonding, reducing the lateral size and improving the efficiency of signal transmission. The flip-chip technique ensures a reliable electrical connection. A square diaphragm with rounded corners is designed and optimised with simulation to sense high pressure based on the piezoresistive effect. The temperature sensing unit with a thin-film platinum resistor measures temperature and provides back-end high-precision compensation, which will improve the precision of the pressure unit. The integrated chip is fabricated by MEMS technology and packaged to fabricate the extremely small integrated sensor. The integrated sensor is characterised, and the pressure sensor exhibits a sensitivity and sensitivity drift of 7.97 mV/MPa and −0.19% FS in the range of 0–20 MPa and −40 to 120 °C. The linearity, hysteresis, repeatability, accuracy, basic error, and zero-time drift are 0.16% FS, 0.04% FS, 0.06% FS, 0.18% FS, ±0.23% FS and 0.04% FS, respectively. The measurement error of the temperature sensor and temperature coefficient of resistance is less than ±1 °C and 3142.997 ppm/°C, respectively. The integrated sensor has broad applicability in fault diagnosis and safety monitoring of high-end equipment such as automobile detection, industrial equipment, and oil drilling platforms. [ABSTRACT FROM AUTHOR]

MEMS devices are more and more commonly used as sensors, actuators, and microfluidic devices in different fields like electronics, opto-electronics, and biomedical engineering. Traditional fabrication technologies cannot meet the growing demand for device miniaturisation and fabrication time reduction, especially when customised devices are required. That is why additive manufacturing technologies are increasingly applied to MEMS. In this review, attention is focused on the Italian scenario in regard to 3D-printed MEMS, studying the techniques and materials used for their fabrication. To this aim, research has been conducted as follows: first, the commonly applied 3D-printing technologies for MEMS manufacturing have been illustrated, then some examples of 3D-printed MEMS have been reported. After that, the typical materials for these technologies have been presented, and finally, some examples of their application in MEMS fabrication have been described. In conclusion, the application of 3D-printing techniques, instead of traditional processes, is a growing trend in Italy, where some exciting and promising results have already been obtained, due to these new selected technologies and the new materials involved. [ABSTRACT FROM AUTHOR]

Micro-Electro-Mechanical System (MEMS) switches have emerged as pivotal components in the realm of miniature electronic devices, promising unprecedented advancements in size, power consumption, and versatility. This literature review paper meticulously examines the key issues and challenges encountered in the development and application of MEMS switches. The comprehensive survey encompasses critical aspects such as material selection, fabrication intricacies, performance metrics including switching time and reliability, and the impact of these switches on diverse technological domains. The review critically analyzes the influence of design parameters, actuation mechanisms, and material properties on the performance of MEMS switches. Additionally, it explores recent advancements, breakthroughs, and innovative solutions proposed by researchers to address these challenges. The synthesis of the existing literature not only elucidates the current state of MEMS switch technology but also paves the way for future research avenues. The findings presented herein serve as a valuable resource for researchers, engineers, and technologists engaged in advancing MEMS switch technology, offering insights into the current landscape and guiding future endeavors in this rapidly evolving field. [ABSTRACT FROM AUTHOR]

In capacitive microelectromechanical system (MEMS) devices, the application of dielectric materials causes long-term charging problems in the dielectric layers or substrates, which especially affect the repeatability and stability of high-performance devices. Due to the difficulties of observation and characterization of charge accumulation, an accurate characterization method is needed to study the effect of charge and propose suppression methods. In this paper, we analyze the influence of charge accumulation on the MSRG and propose a characterization method for charge accumulation based on stiffness variation. Experiments are carried out to characterize the charge accumulation in MSRG, and the effect of temperature on the process is also investigated. In the experiment, the charge accumulation is characterized accurately by the variation of the frequency split and stiffness axes. Furthermore, the acceleration of the charge accumulation is observed at high temperatures, as is the higher additional voltage from the charge accumulation. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication and packaging of RF MEMS switches that have CPW-converted-to-microstrip RF interface at the die level. With microstrip input and output ports the packaging of the dies become greatly simplified, doing away with the need for having off-chip matching and RF transition components inside the package. Two designs are presented, each based on a different philosophy for conversion of the inherent CPW version of the chip to microstrip planar transmission line; i) conversion to microstrip through RF matching, ii) CPW to microstrip on-chip via less transition. Detailed 3D EM simulation based studies were carried out to arrive at the final RF layouts. The switches were fabricated using the silicon on glass architecture and packaged in hermetic RF packages at 1 atm N 2 . Wafer level and post packaging test methods are described. Over the range DC to 10 GHz, the worst case packaged device insertion loss, return loss and isolation are −1.2 dB, −13 dB, −37.5 dB for the first design variant of the switch and are −1.2 dB, −11 dB and −30 dB respectively for the second design variant. The typical pull in voltage is 50 V. [ABSTRACT FROM AUTHOR]

A multilayer (Ti/Pt/Cr/Au) resistive temperature sensor was proposed and investigated to precisely measure the temperature characteristic in microfluidic devices. The Ti/Pt/Cr/Au sensor was fabricated by direct current (DC) sputtering, vacuum evaporation and liftoff process. The thermal annealing test was conducted in the temperature range of 200–800 °C for obtaining an appropriate property of the multilayer. Based on the experimental results, 400 °C was selected as the experimental annealing temperature for the Ti/Pt/Cr/Au layer. The redistribution of structural imperfections and recrystallization promote the density and adhesion of multilayer during the annealing process. With the annealing temperature rising, the annealing process leads to through-thickness migration of chromium and partial depletion of the adhesive layer. The Ti also diffuses into the Pt, which makes the interface disappear. Nevertheless, the layer remains continuous. The temperature coefficient of resistance (TCR) of the sensors was investigated through the microfluidic testing system. The excellent stability and sensitivity of the Ti/Pt/Cr/Au thin-film temperature sensor are verified. Furthermore, the capability of the Ti/Pt/Cr/Au thin-film temperature sensor detecting the sudden temperature change caused by bubble effect is very meaningful to the microfluidic devices. [ABSTRACT FROM AUTHOR]

This paper presents the simulation and analysis of capacitive shunt SPDT RF MEMS switch for high radio frequency applications. The design is based on the shunt configuration consisting of 2 capacitive type switches. To reduce pull in voltage, the high-frequency capacitive SPDT switch is proposed. The beam is designed with non-uniform meanders with perforations. By using the COMSOL Multiphysics tool, we found the pull-in voltage as 1.5 V at a beam thickness of 0.5 μm. The corresponding capacitance ratio is 44 for the dielectric of Silicon Nitrate. The up sate and downstate capacitance of the switch is calculated and simulated. The performance analysis is done by using HFSS tool and is found to RF-perform excellently at 28 GHz with isolation of − 68 dB, the return and insertion losses are − 61 dB and − 0.1 dB respectively. [ABSTRACT FROM AUTHOR]

MEMS switches have a wide range of potential applications in radio frequency and microwave systems due to promising characteristics. However, these devices are still not widespread because of reliability issues. The weak point of the resistive MEMS switch is the contact area that degrades during operation. This paper presents a single-pole double-throw switch having an extended lifecycle due to multiple contact points. The device is based on an aluminum beam suspended on torsion springs. It contains four beams connected to each other and actuated by a common driving electrode. Each beam provides the contact of a platinum bump with a signal electrode at the same contact force. Testing of the four-beam switch and the basic single-beam device is performed in the cold switching conditions. Contact resistance and lifecycle of both devices are analyzed and compared. Degradation of the contact bumps of the four-beam switch and the main failure mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Commercial success of microelectromechanical systems (MEMS) switches is limited by several issues. A high actuation voltage requires special circuitry solutions that increase size and cost of the switch. Another problem is the lack of reliability due to the stiction phenomenon. This paper presents a single-pole double-throw MEMS switch with electrostatic actuation and resistive contact. The device is based on an aluminum beam suspended by the torsion springs over the driving and signal electrodes. The design provides the pull-in voltage as low as 4.9 V. At the same time, the switch is equipped with the mechanism that protects it from stiction. The device is able to operate in the passive and active opening regimes. Recovery of the device after stiction in the hot switching conditions is demonstrated. In the cold mode, stiction is not observed at the transmitted DC power up to 25 mW. The resonant properties and response time of the switch are investigated. The on-resistance and the lifecycle are discussed. The proposed design is characterized by the high mechanical reliability. The main reason of failure is an increase of the on-resistance because of carbon accumulation on the platinum contacts. [ABSTRACT FROM AUTHOR]

The electrostatically actuated MEMS switch with resistive contact is presented. The movable electrode is a beam suspended on its torsion hinges. The contact material is platinum. The switch has an active breaking mechanism making it possible to protect it against stiction and provide a low actuation voltage. The measuring technique for the operating characteristic in the “hot” mode under a low direct current is described. The pull-in voltage and the breaking voltage, the switching time, and the dependence of the contact resistance on the number of actuation cycles are measured. The wear of contact surfaces is investigated. The operation of the switch in a bistable mode is demonstrated, in which the closed condition is maintained without applying the actuation voltage and the state transition occurs due to the active contact breaking mechanism. [ABSTRACT FROM AUTHOR]

The glass polarization effects were introduced in this paper to study the main cause of turn-on drift phenomenon of closed-loop micro-accelerometers. The glass substrate underneath the sensitive silicon structure underwent a polarizing process when the DC bias voltage was applied. The slow polarizing process induced an additional electrostatic field to continually drag the movable mass block from one position to another so that the sensing capacitance was changed, which led to an output drift of micro-accelerometers. This drift was indirectly tested by experiments and could be sharply reduced by a shielding layer deposited on the glass substrate because the extra electrical filed was prohibited from generating extra electrostatic forces on the movable fingers of the mass block. The experimental results indicate the average magnitude of drift decreased about 73%, from 3.69 to 0.99 mV. The conclusions proposed in this paper showed a meaningful guideline to improve the stability of micro-devices based on silicon-on-glass structures. [ABSTRACT FROM AUTHOR]

The structural and electrical properties of Ta2O5/65 nm SiO2 structures with different thicknesses of Ta2O5 varying in the range of 0-260 nm are investigated. We find that the stack structures grown by the magnetron sputtering technique and annealed at 1220 K in O and Ar atmosphere show one of the highest dielectric constant of Ta2O5 (about 64) among those previously reported in the literature. The structure of the annealed polycrystalline Ta2O5 films is orthorhombic, as obtained from X-ray diffraction measurements and we do not observe any preferential orientation of the annealed films. The Ta2O5 films contain positively charged defects which become mobile at around 400 K and they are tentatively correlated with the oxygen vacancies. The leakage current in the stack structures is a factor of 20 higher compared to that in thin layers with 65 nm SiO2. The conduction mechanism in the stack structures can be described by the Fowler-Nordheim model with a barrier height that decreases slightly (<10%) as a function of the thickness of the films. [ABSTRACT FROM AUTHOR]

Currently, the technology of microelectromechanical systems is widely used in the development of high-frequency and ultrahigh-frequency devices. The most important requirements for modern and advanced devices of the ultra-high-frequency range are the reduction of weight and size characteristics, power consumption with an increase in their functionality, operating frequency and level of integration. Radio frequency microelectromechanical switches are developed using the technology of the manufacture of CMOS-integrated circuits. Integrated radio frequency control circuits require low control voltages, the high ratio of losses to the isolation in the open and closed condition, high performance and reliability. This review is devoted to the analytical approach based on the knowledge of materials, basic performance indices and mechanisms of failure, which can be used in the development of radio-frequency microelectromechanical switches. [ABSTRACT FROM AUTHOR]