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The presence of strong ambient vibrations could have a negative impact on applications such as high precision inertial navigation and tilt measurement due to the vibration rectification error (VRE) of the accelerometer. In this paper, we investigate the origins of the VRE using a self-developed MEMS accelerometer equipped with an area-variation-based capacitive displacement transducer. Our findings indicate that the second-order nonlinearity coefficient is dependent on the frequency but the VRE remains constant when the displacement amplitude of the excitation is maintained at a constant level. This frequency dependence of nonlinearity is a result of several factors coupling with each other during signal conversion from acceleration to electrical output signal. These factors include the amplification of the proof mass's amplitude as the excitation frequency approaches resonance, the nonlinearity in capacitance-displacement conversion at larger displacements caused by the fringing effect, and the offset of the mechanical suspension's equilibrium point from the null position of the differential capacitance electrodes. Through displacement transducer and damping optimization, the second-order nonlinearity coefficient is greatly reduced from mg/g 2 to μ g/g 2 . [ABSTRACT FROM AUTHOR]

Microelectromechanical systems (MEMS) thermal-piezoresistive resonator (TPRs) and thermal-piezoresistive oscillator (TPO) use thermal actuation and realize feedback through the piezoresistive effect. They have the advantages of simple manufacturing, high resolution, and low feedthrough. In particular, the piezoresistive effect can be used to realize thermal pumping to extract energy from a power supply and transmit it to the resonance structure. This can significantly improve the effective quality factor of the resonator and even realize spontaneous high-frequency oscillations, which has attracted significant interest from researchers. The combination of self-sustained oscillation with high quality factors of TPRs can perform various sensing applications and give excellent performance. This article provides a detailed introduction to the working principles of TPRs and thermal pumps and discusses methods to optimize their performance. Then, the manufacturing technologies of TPRs are summarized. Finally, applications of the resonators in sensing mass, magnetic fields, and displacement are reviewed. [ABSTRACT FROM AUTHOR]

In this paper, we develop a new approach in order to understand the origin of the quadrature error in MEMS gyroscopes. As the width of the flexure springs is a critical parameter in the MEMS design, it is necessary to investigate the impact of the width variations on the stiffness coupling, which can generate a quadrature signal. To do so, we developed a method to determine the evolution of the stiffness matrix of the gyroscope springs with respect to the variation of the bending beams width of the springs through finite element analysis (FEA). Then, a statistical analysis permits the computation of the first two statistical moments of the quadrature error for a given beam width defect. It turns out that even small silicon etching defects can generate high quadrature level with up to a root mean square (RMS) value of 1220 ° / s for a bending beam width defect of 0.9%. Moreover, the quadrature error obtained through simulations has the same order of magnitude as the ones measured on the gyroscopes. This result constitutes a great help for designing MEMS gyroscopes, as the consideration of the bending beams width defects is needed in order to avoid high quadrature error. [ABSTRACT FROM AUTHOR]

Initial bias is a random parameter in micro-electro-mechanical rate gyroscopes that changes with each turn on and turn off. The bias can be estimated by averaging in static condition or by extended Kalman filter in other conditions. In addition, this parameter is affected by temperature or linear acceleration. Curve fitting on the bias variation of micro-electromechanical rate gyroscopes due to thermal effects is a usual method for thermal compensation of these sensors. However, these approximate curves cannot completely compensate the effect of the thermal bias in long-time applications. In this study, it is tried to improve the calculating accuracy by a combination of extended Kalman filter and the results of these curves and using advantages of both methods. Also bias estimation is improved using the switching algorithm in accelerated motions by avoiding improper data in the estimation process. Experimental tests show the effectiveness of this method especially in long-time accelerated motions. [ABSTRACT FROM AUTHOR]

This paper presents the architecture and optimization verification of a designed mode-mismatching gyroscope prototype made with fused silica in atmospheric pressure. The gyroscope prototype uses the decoupling frame and double-ended tuning fork (DETF) to achieve high sensitivity and quality factor. This structure can suppress residual quadrature error due to fabrication errors and imperfections. The angle rate-sensitive elements of the proposed gyroscope prototype with quasi-digital FM output are two DETF resonators resulting in differential implementation. We describe the principle of operation characterization of our micromechanical vibratory rate gyroscope based on resonant sensing of the Coriolis force and establish mathematical model called multi-parameters excitation system dynamics of Mathieu equation based on our previous work. We specify and quantify the impact functions of mechanical parameters on the properties of gyroscopes and identify sensitivity and limitation of sensitivity and bandwidth each other. A sample-based stochastic model is established to investigate the influence of different uncertain structure size on gyroscope performance. According to the uncertainty analysis, we modify the previous gyroscope structure, and then the parameters and structure of the improved third version gyroscope are obtained. This research can provide a reference for design and optimization of the structure size to improve robustness and performance of resonant angle rate sensor. [ABSTRACT FROM AUTHOR]

In this paper, a novel MEMS tuning fork gyroscope with anchored coupling mechanism is designed to analyze the mode ordering and vibration sensitivity. The proposed TFG prioritizes anti-phase drive-mode by using a levered mechanism while the sense-mode is prioritized utilizing an anchored coupling ring spring linked by four linear beams, which eliminates the lower frequency parasitic mode and provides true mechanical suppression of external vibration. In order to make a contrast with the proposed novel anchored coupling TFG, a conventional one with a direct coupling ring spring between two tines is also designed. The simulated frequencies of the in-phase and anti-phase in the sense mode are 4,006.8 and 4,463.5 Hz, respectively. Meanwhile, the in-phase frequency of the anchored coupling TFG is 5,958.4 Hz, improving by 48.7 %, and the anti-phase frequency is increased a little. Additionally, we carry out the FEM simulations on the vibration sensitivity induced by the stiffness imbalance for the two types of TFGs. Our results demonstrate that the vibration output is reduced by 74.8 and 88.1 % in the anti-phase mode and in-phase mode, respectively. Therefore, the novel anchored coupling TFG can provide improved mode ordering and substantially suppress the vibration output without compromising the scale factor. [ABSTRACT FROM AUTHOR]

This paper focuses on an optimal quadrature error correction method for the dual-mass MEMS gyroscope, in order to reduce the long term bias drift. It is known that the coupling stiffness and demodulation error are important elements causing bias drift. The coupling stiffness in dual-mass structures is analyzed. The experiment proves that the left and right masses' quadrature errors are different, and the quadrature correction system should be arranged independently. The process leading to quadrature error is proposed, and the Charge Injecting Correction (CIC), Quadrature Force Correction (QFC) and Coupling Stiffness Correction (CSC) methods are introduced. The correction objects of these three methods are the quadrature error signal, force and the coupling stiffness, respectively. The three methods are investigated through control theory analysis, model simulation and circuit experiments, and the results support the theoretical analysis. The bias stability results based on CIC, QFC and CSC are 48 °/h, 9.9 °/h and 3.7 °/h, respectively, and this value is 38 °/h before quadrature error correction. The CSC method is proved to be the better method for quadrature correction, and it improves the Angle Random Walking (ARW) value, increasing it from 0.66 ° /'h to 0.21 O/h- The CSC system general test results show that it works well across the full temperature range, and the bias stabilities of the six groups' output data are 3.8 °/h, 3.6 °/h, 3.4 °/h, 3.1 °/h, 3.0 °/h and 4.2 °/h, respectively, which proves the system has excellent repeatability. [ABSTRACT FROM AUTHOR]

A two degrees of freedom (DOF) coupled model is investigated in this paper to analyze the acceleration sensitivity of MEMS tuning fork gyroscopes (TFG) and approaches of decreasing the acceleration sensitivity are presented. Since two tines of TFGs are asymmetric in the mass, stiffness and damping caused by the technological defects, there exists the coupled effect between two tines leading to the invalidity of a single DOF model. Therefore, a two DOFs model is established and the matrix perturbation technique is used to calculate the dynamic responses of the two tines by applying the common-mode acceleration. Our quantitative analysis reveals that the displacement difference is large in the in- and anti-phase modal frequencies between two tines, arising from the unsynchronized motion of two tines due to stiffness imbalance. The FEM simulations coincide with our theoretical calculations. Meanwhile, we take advantage of the experimental data from the other researches to verify our theoretical model and analytical expressions. Our results demonstrate that the acceleration sensitivity of TFGs can be reduced by increasing the coupled stiffness ratio, modal frequency and sense beams widths which are insensitive to technological dispersions. [ABSTRACT FROM AUTHOR]

An author index for the December 2013 issue of the "Journal of Microelectromechanical Systems" is presented.

Through-silicon via (TSV) is one of the key technologies on three-dimensional integration packaging. In this article, an experimental methodology with circuit models was proposed for electrical characteristic tests on typical TSV structures. To this end, self-developed test patterns such as the via chains, the snake interconnections and the Kelvin structures with different dimensions were designed and manufactured. Suitable electrical measurement methodologies were next employed to characterise the element behaviours of the patterns. Based on the experimental data, electrical circuit models for the TSV structures were introduced and the parameters of the model were exacted. The validity and accuracy of the electrical model were finally verified and the TSV characteristic measurements can be performed through a simpler process. [ABSTRACT FROM PUBLISHER]

A compact packaging solution for microelectromechanical systems (MEMS) devices is presented. The 3D-integrated packaging solution was designed for the instrumentation of a spinal screw with a wireless sensor array, but may be adapted for a variety of applications. To achieve the compact package size, an unobtrusive through-silicon via (TSV) design was added to the microfabrication process flow for the MEMS sensor. These TSVs allowed vertical integration of the MEMS devices onto flexible printed circuit boards (FPCBs) using a flip-chip system. Ohmic connections with resistance values below 1 Ω have been achieved for 100 µm TSVs in 300 and 500 µm substrates. This paper describes the design and microfabrication process flow for the TSVs, and provides details on the flip-chip techniques used to electrically and structurally connect the MEMS devices to the FPCBs. [ABSTRACT FROM AUTHOR]

Composition spread analysis of ternary GexSbyTe1-x-y films embedded in an optical multilayer stack close to optical storage application is presented. GexSbyTe1-x-y films with two- dimensional graded composition were deposited in a combinatorial sputter process and analysed with electron-probe microanalysis. Detailed static tester analysis of the crystallisation dynamics are performed in a wide composition range around the pseudobinary line (GeTe - Sb2Te3). Both the as-deposited and the written amorphous phase show a fast crystallisation behaviour within 70-150 and 30-100 ns in a compositional range near the pseudobinary line, respectively. Interrelationship of composition and crystallisation time can directly be imaged from the presented analysis. [ABSTRACT FROM AUTHOR]

This paper presents a micromachined silicon resonant accelerometer based on electrostatic active damping control, which can improve the shock response performance of the accelerometer. In the accelerometer, an electrostatic active damping structure and damping control circuit are designed to improve the equivalent damping coefficient of the system. System-level Simulink modeling and simulation of the accelerometer with an electrostatic active damping closed-loop control link were carried out. The simulation results indicate that the system can quickly return to normal output without an obvious vibration process after the shock. The fabricated and packaged accelerometer was connected to an external test circuit for shock performance testing. The stabilization time of the accelerometer after a 100 g, 3–5 ms half-sine shock was reduced from 19.8 to 5.6 s through use of the damping control. Furthermore, the change in deviation before and after the shock without damping control was 0.8197 mg, whereas it was 0.1715 mg with damping control. The experimental results demonstrate that the electrostatic active damping control can effectively improve the dynamic performance of the micromachined silicon resonant accelerometer. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and characterization of a highly sensitive, single drive multi-axis gyroscope. The multi-axis gyroscope allows for a wide bandwidth in all three axes (X, Y, Z) and exhibits high linearity. The fabricated multi-axis gyroscope was fabricated with a structural thickness of 30 µm and packaged at 100 mtorr using wafer level packaging. The fabricated multi-axis gyroscope has a small footprint of 1426 × 1426 µm2, making it one of the smallest multi-axis gyroscopes. A custom printed circuit board (PCB) was designed for the evaluation of the multi-axis gyroscope. The experimental results demonstrate that the gyroscope has a high sensitivity of 12.56   μ V / dps ,   17.13   μ V / dps and 25.79   μ V / dps in the roll (X-sense), pitch (Y-sense) and yaw (Z-sense) modes respectively. The scale-factor non-linearity of the gyroscope is less than 0.2 % for roll and pitch mode and 0.001 % for the yaw mode, in the full-scale range of ± 1500   deg / s . The multi-axis gyroscope demonstrates an angle random walk of 2.79   dps / Hz , 2.14   dps / Hz , and   1.42   dps / Hz , for the roll, pitch and yaw rate with the in-run bias stability 1.62   deg / s , 1.14   deg / s and 0.84   deg / s respectively. [ABSTRACT FROM AUTHOR]

The oscillation of the sense mode of the micro-machined Coriolis vibratory gyroscope (MCVG) with high quality factor (Q) is analyzed in this study and the corresponding force feedback control scheme is presented to suppress this oscillation. The controller consists of integrator and some filters, instead of the common but complicated demodulation and remodulation modules. Compared with using no oscillation suppression scheme, the proposed simplified oscillation suppression control scheme can achieve an improvement of the sense mode of the MCVG. The inband spectrum ripple of the angular rate output are improved from 51.4 dB to 4.23 × 10−4 dB. Correspondingly, these two performance parameters are improved by 370.4 and 186.2 times, which are higher than two orders of magnitude, respectively. Bias stability is improved from 9.72 deg/h to 2.5 deg/h. Test results prove that the proposed control scheme is effective in suppressing the oscillation. [ABSTRACT FROM AUTHOR]

On-chip integrability of high-Q RF passives alongside CMOS transistors is crucial for the implementation of monolithic radio transceivers. One of the most significant bottlenecks in back-end-of-line (BEoL) integration of MEMS devices on CMOS processed wafers is their relatively low thermal budget, which is less than that required for typical MEMS material deposition processes. This paper investigates electroplated nickel as a structural material for piezoelectrically-transduced resonators to demonstrate ZnO-on-nickel resonators with a CMOS-compatible low temperature process for the first time. Aside from the obvious manufacturing cost benefit, electroplated nickel is a reasonable substitute for polycrystalline or single crystal silicon and thin-film microcrystalline diamond device layers, while realizing decent acoustic velocity and moderate Q. Electroplated nickel has been already adopted by MEMSCAP, a multi-user MEMS process foundry, in its MetalMUMPs process. Furthermore, it is observed that a localized annealing process through Joule heating can be exploited to significantly improve the effective mechanical quality factor for the ZnO-on-nickel resonators, which is still lower than the reported AlN resonators. This work demonstrates ZnO-on-nickel piezoelectrically-actuated MEMS resonators and resonator arrays by using an IC compatible low temperature process. There is room for performance improvement by lowering the acoustic energy losses in the ZnO and nickel layers. [ABSTRACT FROM AUTHOR]

In this paper, ground-signal-ground type through-silicon vias (TSVs) exploiting air gaps as insulation layers are designed, analyzed and simulated for applications in millimeter wave. The compact wideband equivalent-circuit model and passive elements (RLGC) parameters based on the physical parameters are presented with the frequency up to 100 GHz. The parasitic capacitance of TSVs can be approximated as the dielectric capacitance of air gaps when the thickness of air gaps is greater than 0.75 μm. Therefore, the applied voltage of TSVs only needs to achieve the flatband voltage, and there is no need to indicate the threshold voltage. This is due to the small permittivity of air gaps. The proposed model shows good agreement with the simulation results of ADS and Ansoft’s HFSS over a wide frequency range. [ABSTRACT FROM AUTHOR]