Microelectromechanical Structures Research Articles

Control of unmanned aerial vehicle modules based on inertial measurement system and MEMS sensor

This article examines the effect of crosswind on the deflection of UAV cargo in free fall, taking into account the parameters of air resistance and drag coefficient. The displacement results are obtained graphically through simulation. The diagram of the module for stabilizing the load in free fall and the block diagram of the inertial measurement unit (IMU) are described. An analysis of navigation systems was carried out and an IMU was selected that allows the use of dead reckoning (DR) navigation. The principles of operation of inertial measuring microelectromechanical (MEMS) structures are considered. The principles of using IMU and how to configure MEMS sensor data are discussed. IMU accuracy testing has been carried out. A description of the principles of setting up and using a proportional-integral-derivative (PID) controller to control the angle of the stabilizer wing is presented. 3D simulations were performed for the case with and without the stabilization module. The presented results will be useful to UAV developers.

Two-Dimensional Electromechanical Waves in Microelectromechanical Structures (MEMS) with a Nanoscale Gap

Two-Dimensional Electromechanical Waves in Microelectromechanical Structures (MEMS) with a Nanoscale Gap

Acoustic emission in bulk normal and superfluid 3He

We present measurements of the damping experienced by custom-made quartz tuning forks submerged in 3He covering frequencies from 20 to 600 kHz. Measurements were conducted in the bulk of normal liquid 3He at temperatures from 1.5 K down to 12 mK and in superfluid 3He-B well below the critical temperature. The presented results complement earlier work on tuning fork damping in 3He, removing possible ambiguities associated with acoustic emission within partially enclosed volumes and extend the probed range of frequencies, leading to a clearly established frequency dependence of the acoustic losses. Our results validate existing models of damping and point toward the same mechanism of wave emission of first sound in normal 3He and liquid 4He and zero sound in superfluid 3He. We observe a steep frequency dependence of the damping ≈f5.5, which starts to dominate around 100 kHz and restricts the use of tuning forks as efficient sensors in quantum fluids. The acoustic emission model can predict the limiting frequencies for various devices, including micro-electromechanical and nano-electromechanical structures developed for quantum turbulence and single vortex dynamics research.

Dynamic response amplification of resonant microelectromechanical structures utilizing multi-mode excitation

This work presents an analytical and experimental study to enhance the dynamic response of the higher-order vibration modes of resonant microstructures. The detection of higher order vibration modes is usually very difficult due to their low amplitude response, which gets buried in noise. Higher input voltages can be used to enhance the response; however, it is highly energy demanding, can result in electronics problems, and may lead to pull-in of the lower participating modes. In this paper, we present a multi-mode excitation (MME) technique to enhance the vibration response of the higher order modes of an electrostatically actuated micro cantilever beam. First, we derive the dynamic equations of motion of the micro resonator accounting for two electrostatic excitation sources. Then, we apply the Galerkin method to analyze the dynamics of the system analytically. We investigate the effect of using various dynamic AC combinations on the involved modes to yield optimal conditions of the amplitude magnification. Then, an experimental investigation is conducted based on a micro resonator made of polyimide. The results showed that, compared to the single mode excitation (SME), the MME can significantly raise the level of the response above noise and amplify the displacement amplitude to yield a higher signal-to-noise ratio. The maximum displacement amplitude can be amplified multiple times as determined by the AC loads. Hence, the improved displacement amplitude with the proposed technique makes it promising for future signal processing technologies and for realizing high-sensitivity sensors.

Multifunctional fiber-optic sensors for space infrastructure

Sensors used in rocket and space technology are subject to extreme external influences in terms of temperature, vibration, and shock. Therefore, the choice of the type of sensors is justified precisely by the resistance to such factors, as well as the ability to ensure the temporal and parametric stability of measurements. A new type of sensors – fiber-optic ones – meets these conditions. The basis for the selection and further improvement of such sensors were such requirements as minimum power consumption, high accuracy and stability of measurements, the ability to combine several measurements in one sensor. It is noted that for space infrastructure the factor of the possibility of simultaneous measurement of several parameters with one sensor is one of the important quality indicators. This is due to the possibility of reducing the number of sensors themselves, which reduces the mass and size parameters of space technology. This applies, first of all, to measurements of pressure and temperature, since they, in aggregate, account for at least 40 % of all measurements in space products. The path of choos-ing the types of methods and sensor designs led to the combination of the amplitude conversion method and optical communication in one sensor. In this case, amplitude modulation of pressure and temperature is carried out by a microelec-tromechanical unit (module), and the modulated optical signal is transmitted by an optical module. Such a modular composition of the sensor makes it possible to dispense with optical ana-lyzers (interrogators) and carry out further pro-cessing based on standard interfaces. A limitation of the proposed methods and designs is the need for microelectromechanical structures that measure certain physical quantities. Such structures for fiber-optic sensors are not mass-produced; therefore, their manufacture can be established at instrument-making enterprises with microelectronic equipment

Stresses modeling in multilayer semiconductor structures of automobile regulators and predicting the reliability of their operation

The problems of increasing the reliability of microelectromechanical systems are considered on the example of an automobile voltage regulator. A model of the process is proposed and a study of the effect of temperature on the formation of stress fields in semiconductor structures of active elements of the controller is carried out. The studies assumed of a possible reason for the change in the parameters of the regulator due to the appearance of defects in the crystal structure of the semiconductor material in the structures of integrated voltage regulators. For the study, a mathematical model was proposed that describes the behavior of a semiconductor element of a real car voltage regulator. It was found that the distribution of stresses in the structures is uneven and the maximum value of stresses reaches the edges., An increase in temperature gradients in the structures of regulators leads to the formation of dislocations that change the electrical characteristics of devices. As a result of modeling, it has been established that thermoelastic stresses arising in the process of manufacturing and functioning of semiconductor structures of a regulator in regulators of this type can cause a change in the structure of a semiconductor device due to relaxation of elastic stresses at dislocations. in cars. Measures are proposed, including thermostating of the sensitive elements of microelectromechanical structures, which will increase their service life.

Silicon‐Based Terahertz Meta‐Devices for Electrical Modulation of Fano Resonance and Transmission Amplitude

AbstractSeeking active and effective control over electromagnetic waves has always been an important focus in optics. Fano resonances occur in planar terahertz (THz) metamaterials by introducing a weak asymmetry in a two‐gap split ring resonator. Without extra layers of photoactive materials and microelectromechanical structures, a novel and economical scheme based on silicon‐integrated THz asymmetric metallic split ring metamaterial is proposed to control Fano resonance and transmission amplitude via electrical excitation. The results show that Fano resonance and transmission amplitude abate drastically with the increase of current bias, due to the loading of electrically formed silicon carrier layer. As the current bias is increased, both the thickness and conductivity of silicon carrier layer are modulated simultaneously. The depth range of modulated silicon carrier layer could reach 250 µm. Besides, a THz transmission amplitude modulator with a modulation depth of 93% is also demonstrated. This work significantly expands the function of silicon‐based metamaterials and opens up opportunities for the realization of switchable sensors, filters, and nonlinear devices.

Fabrication of Area Effective Silicon Membrane By Frontend Bulk Micromachining for High Pixel Density Thermal Imager Array

The fabrication of Silicon membrane by frontend bulk micromachining process has been proven to be one of the simple and cost-effective technique, for fabricating microelectromechanical structures. In this paper, we propose novel geometric mask designs, to be used as a pixel for Microbolometer application, for achieving highly reliable and area-efficient microstructures by frontend Silicon (Si) bulk micromachining. In the proposed design, all the rectangular openings are aligned at 45⁰ with respect to the wafer primary flat (100) of the Silicon wafer, such that only <100> planes are exposed and etched during anisotropic etching. However rectangular openings lead to high silicon area consumption which makes the process unworthy. Therefore, we proposed different geometries to minimize area consumption for achieving the same dimension of suspended structure. The fabrication of these Silicon membranes, to be used as Microbolometer pixels were simulated using Intellisuite FABSIM based physical simulator by two different techniques, one involving only wet chemical etching (called Method I) and the other involving dry-cum-wet etching process (called Method II). The simulation result shows an 86% reduction in footprint by Method II over the basic mask design when compared with the Method I, thus making it suitable for high pixel density thermal imager array. Thermal imaging is an established technique to convert the invisible radiation pattern emitted by an object into visible images, without establishing contact with the object, for feature extraction and analysis. Though Infrared thermal imaging was first developed for military purposes, it later gained a wide application in various fields such as aerospace, agriculture, civil engineering, medicine, and veterinary and many more, which is left to the researcher's imagination to explore its diverse applications in near future. It can be applied in all fields where temperature differences could be used to assist in the evaluation, diagnosis, or analysis of a process or product. Thus from agriculture and food industry perspective, thermal imaging technology can have the following potential applications: predicting water stress in crops, planning irrigation scheduling, disease and pathogen detection in plants, predicting fruit yield, bruise detection in fruits and vegetables, evaluating the maturing of fruits, detection of foreign bodies in food material, grain storage & drying, etc. Finally, as a proof of concept, we fabricated a single-pixel Silicon membrane using the proposed Method I as per the process flow outlined in the paper. Both simulation and experimental result shows very good agreement on all process steps. The fabricated Silicon membrane which acts as a mechanical platform is monolithic, as it does not involve any sacrificial layer, thus making it highly robust and reliable, as a result, it can be used for diverse sensing applications. Figure 1

Formation of out-of-plane film micro arch by methods of technological control of internal stress

In this work is presented the analysis of the manufacturing technology of arcuate elastic elements. In the course of the work, the technological problems of the formation of out-of-plane microelectromechanical structures with the use of surface micromachining were studied. Internal stresses were controlled by varying the pressure of the working gas during sputtering. The use of this method allowed forming the arcuate profile of the Cr-Cu-Cr film structure.

Enhancement of Micro cantilever’s Rectangular and Triangular Beam for Improvising the Sensitivity of Biosensor – a Comparative Study

Micro-Electro-Mechanical Systems (MEMS) is the mixing of factors like mechanical, sensors, actuators, and electronics on a common substrate through the consumption of micro-fabrication era or micro-technology. A type of beam is called “cantilever” which provides assistance at only one end. This work affords to have a look on MEMS based entirely micro cantilever beama which are employed in medical software systems and are a component to slicing region reasonably evolved sensors. The beams of the Cantilever are the most omnipresent systems within the area of micro-electromechanical structures (MEMS). MEMS cantilevers are normally made from silicon (Si), silicon nitride (Si3N4), or poly-silicon. A procedure on growth in deflection of micro cantilever beam is essential for enhancing the sensitivity of biosensor. The sensitivity level of a microcantilever biosensor relies upon on its deflection that occurs because of the antigen-antibody interplay. The deflection can be elevated by way of growing the length or lowering the thickness of micro cantilever beam but it’ll minimize the reverberating frequency of the beam. This minimizes the resonant frequency and that makes the cantilever vulnerable to thermal noise and low frequency vibrations which immediately affect the size of deflection. In this method, the rectangular and triangular shapes are taken into consideration and the comparative evaluation is established. The outcomes display that the deflection of triangular beam is two times extra than rectangle fashioned beam.

Laser-assisted stress reduction in molybdenum microstructures for CMOS compatible MEMS integration

The fusion of micro-cantilevers over complementary-metal-oxide-semiconductor (CMOS) wafers (with driving electronics) is essential integration requirement for the development of portable sensing devices. In general, the stress gradient in metal cantilevers (after release) lead to structure warping and limits the performance and stability of the final fabricated devices. This work is focused to solve the requirement of (i) having a stress-free metal based micro-electro-mechanical structures (MEMS) without using high-temperature annealing technique and (ii) process compatibility with vapor HF release. We demonstrate a laser-assisted stress controlling scheme to achieve free-hanging metal cantilever without affecting the underneath (essential requirement for CMOS-MEMS integration) deposited layers. The molybdenum (Mo) metal is deposited by physical vapor deposition (PVD) technique at the temperature of 200 °C and then patterned to obtain the microcantilever beams of different length. High-pulse-energy excimer laser (wavelength =248 nm with pulse duration =24 ns) is used to anneal these metal cantilevers and their residual stress is measured by analyzing the final displacement of the released microbeams. Different laser energy density ranging from 200 × 10−3 J/cm2 to 450 × 10−3 J/cm2 is used to study the optimized parameters in the annealing process. Proposed pulsed laser-annealing (PuLA) technique reduces not only the stress gradient but also aid stress-tuning ability that has numerous advantages especially in electrostatic and piezoelectric MEMS devices. Furthermore, we also present the impact of laser action on the grain microstructures and electrical conductivity. Results show that molybdenum microstructures with localized laser heat treatment achieve a reduced surface roughness (from 7.5 nm to 3.8 nm) and improved electrical conductivity. Results demonstrate that the proposed PuLA scheme is a promising technique for (i) eliminating stress in metal interconnects in CMOS-MEMS integrations, (ii) building a stress-free and smooth surface micromechanical platform for N/MEM (resonators, sensors and actuators) devices and (iii) establishing molybdenum as an anti-diffusion barrier in Cu interconnect technology owing to its excellent bulk property.

Micro-Sensor Design Considerations for Desired Operational Range Based on Piston Coupled Diaphragm

In this paper, sensor and actuator design rules are obtained for designing a piston coupled diaphragm (PCD), which is then formulated based on physical science and engineering theories. This PCD structure has advantages, such as piston-like motion under loading, isolated electrical and mechanical parts, and designable electrodes area. It has the potential to be widely used in microelectromechanical system structures in future. Since this type of structure is a new structure in engineering, the formulation of PCD is important for designing sensors and actuators. Deflection under electrostatic force is derived, and the expression of pull-in voltage is obtained. Next, its accuracy is verified through finite-element simulation, and von Mises stress of structure is obtained, and the maximum pressure to avoid yield stress of the material is studied. The nonlinear and linear behavior of the structure is obtained, and a factor to be in the linear region in relation to the thickness is defined. Subsequently, a gap-to-thickness ratio is discussed by considering electrostatic issues and readout challenges. Finally, the theoretical results are verified by simulation results, indicating a maximum error of 4.9% from pull-in voltage and 8.5% error from stress results.

Modeling of a High-Frequency Microelectromechanical X-Band Switch for Space Applications

The results of modeling of microwave and mechanical characteristics of an X-band switch based on the technology of high-frequency microelectromechanical structures are presented. A method for design of a device operating directly in the external environment and a device whose moving components are placed in a dielectric case. Characteristics of the optimized switches are determined. Estimated mechanical calculations confirming high stability of the developed high-frequency microelectromechanical structure switches in the temperature range specific of devices used in the space industry are also performed.

Nanoindentation response of monocrystalline copper under various tensile pre-deformations via molecular dynamic simulations

The mechanical properties of a material can be positively or negatively affected by its applied or residual stress. In this article, a series of molecular dynamic simulations were adopted to investigate the nanoindentation response of monocrystalline copper under tensile pre-deformation. Nanoindentation simulation under stress-free condition was compared with those under pre-tension strain values of 1.2%, 2.4% and 3.6%. Load–displacement curves with hardness value and recovery rates of total work for nanoindentation based on various tensile pre-deformations were obtained and discussed. It indicated that tensile pre-deformations resulted in a higher potential energy in substrate and a lower external energy will be introduced to realize the same elastic or plastic deformation during indentation. Moreover, the evolution of interior defects during indentation was also observed and analysed. The results showed that tensile pre-strain can influence dislocation nucleation behaviour of material during indentation. This article proposed a special molecular dynamic simulation method to characterize the mechanical properties of the material under tensile pre-deformations via nanoindentation, which gives an effective approach to characterize residual stresses in micro- and nanoscale and will have promising application in mechanical characterization of Microelectro Mechanical Systems devices and structures. Further analysis based on experiments will be done in our further research work.

METHODS OF IMPROVING ACCURACY OF MEASURING OUTPUT CHARACTERISTICS OF TENSOMETRIC ELEMENTS AND TESTMODULES

Over the past few years, thanks to the success of microprocessor technology, there has been a significant leap in the development and application of automated control systems. In such systems, information obtained from a set of sensors installed on the control object and giving complete information about it is used to form the control action. Improving the accuracy of measurement of their characteristics becomes an urgent task. This paper is considered to study of the processes of degradation of microelectromechanical structures of integral measuring tensometric elements, for example, pressure sensors, expressed in the obtaining of the output characteristics of the sensor for the regulations set forth in the technical specifications. The technique allowing to measure the parameters of the output signal of the strain cell with the help of a special installation is developed. The results of the experiments determined that when using material with a small modulus of elasticity can be used for the planting element, any substrate material of test module. The developed technique can be used in the production and design of the strain gauge, and the sensor as a whole.

ДОСЛІДЖЕННЯ МІКРОЕЛЕКТРОМЕХАНІЧНИХ П'ЄЗОЕЛЕКТРИЧНИХ СТРУКТУР МЕТОДОМ АТОМНО-СИЛОВОЇ МІКРОСКОПІЇ

Currently leading manufacturers of electronic components serially produce a rather extensive list of elements, in which various microelectromechanical structures are included, such as various accelerometers, which are produced by millions of copies, resonators and electrical signals filters implemented on their basis, transformers and other microminiature electromechanical systems. The main advantage of using of elements, made of piezoceramic materials, in measuring devices is determined by their special structure, which allows to implement in one such element fundamentally different schemes, for example, for simultaneous measurement of temperature, pressure and humidity. The purpose of the work is to investigate hidden microdefects and microroughnesses of the surfaces of piezoelectric transducers using atomic force microscopy.

ДОСЛІДЖЕННЯ ЕЛЕКТРИЧНОГО ІМПЕДАНСУ П'ЄЗОЕЛЕКТРИЧНОГО ДИСКА З СЕКТОРНИМИ ЕЛЕКТРОДАМИ

Currently leading manufacturers of electronic components serially produce a rather extensive list of elements, in which various microelectromechanical structures, such as various accelerometers, resonators and electrical signals filters implemented on their basis, transformers and other microminiature electromechanical systems, are included. Piezoelectric disks with partial covering by electrodes of one or two surfaces are often used to create various functional piezoelectronic devices. Disks with sector covering by electrodes are almost the main element of many microelectromechanical systems. The purpose of this article is to research electrical impedance of disk piezoceramic transformers with sector electrodes

Design and simulation of RF MEMS comb drive with ultra-low pull-in voltage and maximum displacement

Comb drive actuators are very important microelectromechanical systems structures that are widely used in many applications. They are currently used in force balanced accelerometers, resonant accelerometers and resonant gyroscopes, micro-grippers and micro-engines. In addition, they are extensively used in opto-mechanical subsystems such as switches and variable optical attenuators. The goal of this paper is to present a comb drive actuator model design with ultra-low pull-in voltage to achieve large displacement, deriving the exerted forces equations, mechanical analysis and the most important problems, also comparing with the previous work done to treat these problems.

Nonlinear Thermoelectroelastic Analysis of III-N Semiconductor Devices

The diffusion-drift electron transport description is combined with finite deformation theory to model thermoelectroelastic behaviors in piezoelectric semiconductors under conditions when the mechanical strains/displacements are not small so that the usual assumption of linearity cannot be justified. The nonlinear treatment includes both kinematic and constitutive corrections as well as a proper treatment of the electrostatic conditions at free surfaces. The theory is illustrated using numerical simulations of various III-N devices of technological interest, including of conventional AlGaN/GaN HEMTs and of semiconducting microelectromechanical structures that can require the nonlinear theory’s rotational invariance even when the strains are small. Despite uncertainties in the values of the various material coefficients, it seems likely that the nonlinear corrections are often substantial.

Design and optimization of a three-terminal piezoresistive pressure sensor for catheter based in vivo biomedical applications

In recent times, catheters with integrated transducers have been extensively investigated in the field of biomedical engineering, especially for use in in vivo neonatal intensive care systems. An integral module of such systems is a blood pressure sensor that must fulfill the competing requirements of high sensitivity and small area. Typically, microelectromechanical systems-based membrane structures with integrated piezoresistors are used to realize such miniaturized blood pressure sensors. Conventionally, the electromechanical transduction of membrane deformation into an equivalent electrical signal is accomplished by piezoresistors connected in a fully active Wheatstone bridge configuration. However, such a configuration requires a large area for the placement of piezoresistors and layout of interconnects. Even though piezoresistors connected in a half-active Wheatstone bridge configuration overcome the area constraint, such an arrangement still suffers from reduced electrical sensitivity. In this paper we propose a novel three-terminal single-element piezoresistor membrane-based miniaturized blood pressure sensor for less than 1 French catheter application. Design and optimization of the sensor is performed using numerical simulations to satisfy the competing requirements of high sensitivity, low structural non-linearity and high mechanical stability. Simulations are carried out to optimize the piezoresistor position, piezoresistor doping concentration and relative dimensions of the piezoresistor and the membrane. Results depict that sensor with a die size of 175 × 150 × 50 μm3 results in an electrical sensitivity of 14.03 μA A–1 mmHg–1. Finally, a set of design guidelines are outlined for optimizing the performance of three-terminal piezoresistor-based blood pressure sensors.