CoventorWare Software Research Articles

Design and Simulations of High-Sensitivity Multi-Directional Inertial Sensor

This paper proposed the high sensitive linear and rotational based differential capacitive inertial sensor. The designed sensor consists of a proof of mass, which resides in an air medium — the acceleration measured along with a change of displacement and the differential capacitance. Sensor modeling and simulation have done with CoventorWare software. SOIMUMPS fabrication process has described because it allows pattern on both sides of an SOI wafer. Solid mechanics and electrostatic analysis have applied for measurement of acceleration. The high sensitivity of 981.28fF/g has observed. The simulated results have tabulated. Finally, performance and future scope of the inertial sensor has discussed.

Manufacturing and Testing of Radio Frequency MEMS Switches Using the Complementary Metal Oxide Semiconductor Process.

A radio frequency microelectromechanical system switch (MSS) manufactured by the complementary metal oxide semiconductor (CMOS) process is presented. The MSS is a capacitive shunt type. Structure for the MSS consists of coplanar waveguide (CPW) lines, a membrane, and springs. The membrane locates over the CPW lines. The surface of signal line for the CPW has a silicon dioxide dielectric layer. The fabrication of the MSS contains a CMOS process and a post-process. The MSS has a sacrificial oxide layer after the CMOS process. In the post-processing, a wet etching of buffer oxide etch (BOE) etchant is employed to etch the sacrificial oxide layer, so that the membrane is released. Actuation voltage for the MSS is simulated using the CoventorWare software. The springs have a low stiffness, so that the actuation voltage reduces. The measured results reveal that actuation voltage for the MSS is 10 V. Insertion loss for the MSS is 0.9 dB at 41 GHz and isolation for the MSS is 30 dB at 41 GHz.

A new improved vertical comb type differential capacitive sensing micro accelerometer using silicon-on-insulator wafer technology

A new and improved approach using vertical combs for the differential capacitive sensing of acceleration using silicon-on-insulator (SOI) wafer technology is presented. The design, which supports a ± 30 g operational range demonstrates the enhanced linear range that is achievable using an SOI approach, which overcomes the limitations of the dissolved wafer process (DWP) technology based on the diffusion layer depth in silicon, used for the fabrication of MEMS accelerometers. Two technological approaches are compared, one having the same thicknesses of fixed and movable interdigitated fingers (DWP) and the other having different thicknesses, using an SOI wafer. A remarkable sensitivity improvement, by a factor of up to two, is achieved for the capacitance change per unit g (deltaC g−1) using the new differential SOI design presented here. The bandwidth of the device is also improved significantly in the SOI design, compared to the DWP design. Furthermore, the effect of temperature (−40 °C to 125 °C) has an almost negligible influence on (deltaC) due to the built-in differential concept of comb-type fingers compared to DWP technology. Cross-axis sensitivity is also very low due to the stable, robust design of the accelerometer offering less stiction sideways and better pull-in stability. Simple analytical relations for dynamically changing overlap capacitance are derived and presented. These analytical results are compared with simulations using Coventorware software and are in agreement to within 1.8% in a linear range of operation up to a tip deflection of 8.5 µm. The effects of fabrication tolerances, including all the process steps, on the sensitivity (deltaC g−1) and bandwidth (BW), are also studied and the results presented. An overall figure of merit (FOM) is included which is better in this study compared to the available literature. Furthermore, only two wafers are needed to fabricate the proposed differential capacitive sensors, compared to conventional push–pull three plate systems using three wafers. A separate deep reactive ion etching (DRIE) step on two different wafers offers better debris removal as compared to the interdigitated fingers cut by a single DRIE step.

Design and Simulation of Micro Tactile Sensor for Stiffness Detection of Soft Tissue with Irregular Surface

Tactile sensors become an essential part of many applications in our life. Integrating tactile sensors with surgical tools used in MIS is significant to compensate for the shortage of touch feeling of soft tissues and organs comparing with traditional surgeries. This paper presents a detailed design of a micro tactile sensor for measuring the stiffness of soft tissue with an irregular surface. The sensor consists of five cantilever springs with different stiffness. A spring in the middle has a relatively low stiffness surrounded by 4 springs have relatively equal high stiffness to compensate for the soft tissue contact error in the longitudinal and lateral directions. Sensor parameters are selected to ensure high sensitivity and linearity with taking into consideration the cross-talk effect among the sensor springs tips. A detailed design of the sensor structure in the microscale is conducted based on some constraints related to MEMS fabrication. A finite element analysis (FEA) of the sensor structure is conducted to evaluate sensor structure performance using CoventorWare software. Then, an FEA for the piezo-resistors, as a signal transduction method, is conducted which maps the sensor output to an electrical signal. The results prove that the sensor can differentiate among different soft-tissue stiffness within the selected range independent of the applied distance between the sensor and the tissue with an error below 3% even with inclination angle between the sensor and the tissue ±3°. Furthermore, a linear performance has been achieved between the soft-tissue stiffness and the sensor output.

Effect of seismic mass thickness on the resonance frequency of cantilever type piezoelectric energy harvester

Piezoelectric energy harvesters find applicability in remote area of application because of simple design and operation. Micro-electromechanical system (MEMS) process technology is utilized to fabricate these cantilever based structures. Piezoelectric layer length and thickness are the key parameters for controlling the resonance frequency. However, for further lowering the resonance frequency and having optimal output a seismic mass is introduced at the tip of the cantilever structure. In this paper, the effect of increasing the thickness of the seismic mass on the resonance frequency of the cantilever structure has been investigated. Finite Element Method (FEM) results have been obtained using Coventorware software by varying the thickness of the seismic mass 10–20 µm. It has been observed the variation of the thickness of the seismic mass has an effect on the resonance frequency of the cantilever. As the thickness increases, the volume of the seismic mass increases and the resonance frequency of the cantilever decreases. The base of the cantilever is Silicon; Aluminum Nitride (AlN) piezoelectric material has been selected of 3 µm thickness. The length of the silicon cantilever is varied from 1600 to 2500 µm and the resonance frequency is obtained. At a length of 1600 µm, variation of seismic mass thickness from 10 to 15 µm results in reduction in resonance frequency by 17.27% whereas when seismic mass is varied from 15 to 20 µm the resonance frequency is reduced by 12.63%.

Effects of various loading on the performance of MEMS cantilever beam for in-field tuning of sensors and actuators for high temperature and harsh environment applications

MEMS devices require active mechanism for tuning in field operation because post fabrication, design parameters may change due to residual stress, fabrication imperfections, temperature etc. Application of axial compressive (C) or tensile forces (T) allows one to implement this tuning. Effects of C and T forces, stress gradient (SG) and transverse loading is analyzed for futuristic materials like Gallium Nitride (GaN) and Silicon Carbide (SiC) for use in high temperatures and harsh environments. The effects of above forces on pull in voltage (VPI), bandwidth (BW) and resonance frequency (RF) are analyzed. Results for Aluminum cantilever beam show, that VPI decreases by ~ 1.2 times at low beam lengths of 200 µm and about 5 times at higher length of 800 µm when T force is changed to C under loading. Similar trends are holding for GaN and SiC except that VPI scales up in proportion to material’s Young’s modulus E. An analytical relations of VPI versus E and Poisson’s ratio‘ν’ are predicted. Effect of SG is also studied and it is found that although SG affects VPI within 10% range, application of axial C or T forces further change it within 20% range. Comparison of analytical results for VPI with Coventorware software shows a better agreement for low loading of 10% compared to full loading of 100%. Also, Log–Log plot of VPI versus L can be used to estimate the contribution of charge re-distribution and fringing field. Furthermore, BW decreases by 16 Hz when C is applied and increases by 66 Hz when T is applied for Aluminum cantilever with 400 µm length and 50 µm width. Similarly, RF decreases by 165 Hz in C and increases by 623 Hz for T loading. The predictions of our model agree well with experimental and FEM results (within 4.54% and 6.46% respectively).

Design of tunable interdigital capacitor

In this paper, a MetalMUMPs (Multi-User Microelectromechanical System Processes) based tunable interdigitated capacitor is proposed. The tunable interdigitated capacitor consists of thermal actuator, guided beam, and twelve closely coupled parallel fingers lines to produce a nominal capacitance value of about 40.863 fF capable to tune till 326.902 fF. It actuated (tunned) thermally by applying a voltage across the thermal actuator to decreased distance between capacitor rotor and stator then capacitor becomes more capacitive, due to the increase in fringing fields between the fingers. The tunable interdigitated capacitor was fabricated on a standard low-resistivity substrate adopting MetalMUMPs manufacturing process. It was suspended by 25μm from the inner surface of the etched silicon substrate. It typical called microstrip tunable interdigitated capacitor. The capacitor was designed using 2008 CoventorWare software and fabricated based on MetalMUMPs technology. The measured capacitor structure is 494×520 μm2. The measured results show good compatible with theoretical one.

A high performance multiband BAW filter

In this paper, a multi band filter using TFBAR is proposed for 4G/LTE IEEE standard at mobile front end terminal. Initial layout of FBAR is designed and analyzed in Coventorware software. The electromagnetic properties and equivalent circuit characteristics of proposed multi-band filter are studied using Advanced Design System, Agilent software. The filter works well for frequency range 2.3–2.4 and 1.97–2.24 GHz. In this research work, the effect of inserting passive elements i.e. inductor (L) and capacitor (C) either alone or both in series and shunt arms of equivalent circuit of filter are also studied. As a result of introducing LC components, the filter responses at different frequency range and converges the frequency response either narrow or wideband of the proposed filter. The measured insertion loss is better than − 2 dB and return loss is better than − 20 dB. The novelty of this work is designing of miniaturized multiband filter which can be deployed in future mobile RF front end terminal that not only cover upcoming frequency band but also cover present standard IEEE communication band.

ANN Modeling of Motional Resistance for Micro Disk Resonator

This article describes how modeling is an integral part of design and development of any system that provides the theoretical characterization of the system and helps in understanding the relations between various parameters of the system, before the system is developed. The capability of an Artificial Neural Network (ANN) to model the complex relations between a set of inputs and outputs is exploited to model the motional resistance and resonance frequency for a contour mode disk resonator. The solution was to develop a multilayer feed forward neural network. The data set required to train the ANN is obtained by developing an electrical equivalent model and through the MEMS simulation software Coventorware. The network is trained using a Levenberg Marquardt algorithm. The number of hidden layers and the number of neurons in each hidden layer is optimized using a genetic algorithm. The ANN model developed an efficient model of the motional resistance and resonance frequency of the disk resonator. The ANN output is compared with the output of an electrical equivalent model and a reported fabricated structure.

A novel method for finding the best excitation frequency of MEMS vibratory gyroscope

In this paper, a novel method is proposed for finding the best excitation signal frequency of the MEMS vibratory gyroscope sensors. In the proposed method, the amplitude of the drive mode displacement is the criterion to choose the proper excitation signal frequency. To assess the performance of the proposed method in comparison with other common ones, a PLL-based control loop is designed and simulated. According to the nonlinear behavior of the gyroscope, the excitation signal frequency would not converge and will oscillate within a 15 Hz range using the PLL-based control loop. To resolve the disturbing oscillations, an effective approach is proposed in which the frequency excitation signal will be constant and the drive mode amplitude will stop oscillating. The proposed method finds the best excitation frequency accurately. To this aim, a 2-degrees-of-freedom MEMS vibratory gyroscope is designed and simulated by CoventorWare software. To reflect the nonlinear behavior of the sensor, all the elements are considered nonlinear. The simulation results show the superb advantages of our proposed method in comparison to the classic state-of-the-art solutions.

Characterization of embedded microheater of a CMOS–MEMS gravimetric sensor device

A CMOS–MEMS device for mass detection has been designed using 2008 CoventorWare software and fabricated using 0.35µm CMOS technology. This paper reports the characterization of the microheater and the temperature sensor embedded in the device. The measured resistances of the microheater and the temperature sensor were found to be close to the modeled values within ~4.2% error. The average temperature coefficient of resistance (TCR) of the temperature sensor of five dies was determined by increasing or decreasing the temperature in a range of 25°C–100°C. The resistance of the temperature sensor was found to increase with either an increase in ambient temperature or the voltage applied to the microheater, with a correlation factor of 0.99. The average TCR was found to be 0.0034/°C for the increasing temperature and 0.0036/°C for the decreasing temperature as compared to 0.0037°C reported in the literature, indicating an error of 8.1% and 3.5%, respectively. These differences between the measured and reported values are believed to be due to fabrication tolerances in the design dimensions or the material properties. The humidity was found to have a negligible effect on the resistance of the temperature sensor for increasing humidity levels from 40% to 90%. The repeatability of the measurements has shown low standard errors, which gives confidence in the reliability of the fabricated device.

Fabrication of a Micromachined Capacitive Switch Using the CMOS-MEMS Technology

The study investigates the design and fabrication of a micromachined radio frequency (RF) capacitive switch using the complementary metal oxide semiconductor-microelectromechanical system (CMOS-MEMS) technology. The structure of the micromachined switch is composed of a membrane, eight springs, four inductors, and coplanar waveguide (CPW) lines. In order to reduce the actuation voltage of the switch, the springs are designed as low stiffness. The finite element method (FEM) software CoventorWare is used to simulate the actuation voltage and displacement of the switch. The micromachined switch needs a post-CMOS process to release the springs and membrane. A wet etching is employed to etch the sacrificial silicon dioxide layer, and to release the membrane and springs of the switch. Experiments show that the pull-in voltage of the switch is 12 V. The switch has an insertion loss of 0.8 dB at 36 GHz and an isolation of 19 dB at 36 GHz.

The design and analysis of a MEMS electrothermal actuator

This paper introduces a type of out-of-plane microelectrothermal actuator, which is based on the principle of bimetal film thermal expansion in the fuse. A polymer SU-8 material and nickel are used as the functional and structural materials of the actuator. Through heating the resistance wire using electricity, the actuator produces out-of-plane motion in the perpendicular axial direction of the device and the bias layer contact with the substrate, completing signal output. Using Coventorware software to establish the three-dimensional model, the geometric structure is optimized and the electrothermal capabilities are determined theoretically. From electrothermal analysis, the actuator's displacement is 18 μm and the temperature rises from 300 to 440 K under a voltage of 5 V and the response time is 5 ms. The actuator's displacement is 20 μm under a 100000 m/s2 acceleration in the accelerating field. In the coupled field, applying a 3 V voltage, the initial temperature is 300 K, while the acceleration is 50000 m/s2, the driving displacement of the actuator is 23 μm, and temperature rises to 400 K. Finally, through checking the stress in different field sources, the maximum stress of the actuator is smaller than the allowable stress of nickel. The results show that the electrothermal actuator has high reliability.

MEMS Carbon Nanotubes Field Emission Pressure Sensor With Simplified Design: Performance and Field Emission Properties Study

The pressure sensor application gained recently substantial interest in many fields of basic and applied research and applications. In this paper, microelectromechanical system (MEMS)-based pressure sensor contains nanostructured electrode consisting of carbon nanotube (CNT) array. CNTs are directly grown on such electrode by plasma-enhanced chemical vapor deposition method using microwave plasma torch at atmospheric pressure. This growth method enables us to use a simple electrode structure without need of buffer layer and time-consuming lithography process. Combination of CNTs field emission and MEMS membrane mechanical properties make possible to enhance sensitivity of the sensor. Field emission properties of CNTs are measured by newly developed system enabling us precise measurement of expecting properties, such as dependence on diaphragm (upper electrode) distance, applied voltage, and stability of the sensor. Measured values are compared with a numerical modeling of the membrane system in Coventor Ware software by finite-element method. We also suggest encapsulating the sensor using glass frit bonding because such method is more suitable for high vacuum requirements of the field emission operation.

MEMS switches for 0.1–40 GHz for Pico-satellite application

This paper deals with the RF (Radio Frequency)-MEMS (Micro-Electro-Mechanical-System) switches are integrated in CPW topology. Phase shifter is integrated on high resistivity silicon substrate and loading elements are 360 switch design using the coventorware software and its superiority over the existing technologies like PIN Diodes and Field-Effect-Transistors regarding size, power, Isolation The measured down state insertion loss of ?0.1 dB up to 40 GHz and switch resistance is 1 ?. The measured reflection coefficient is dominated bt t-line switch is ?20 dB at 30 GHz. This switch used in X-band and K-band phase shifter, switched capacitor bank and tunable filter. The 1-kg class satellite plans to use the MEMS TxRx switch as a functional component on its RF communication board. Application of switch based Phase shifters for satellite based radars (20 billion cycles), missile systems (0.1---1 billion cycles), long-range radars (20---200 billion cycles). By cutting the mass of components onboard the space vehicle, the launch costs and hopefully the overall budget for production can be reduced.

CANTILEVER TYPE SWITCH DESIGN

This paper deals with the RF (Radio Frequency)-MEMS (Micro-Electro-Mechanical-System) switch design using the coventorware software and its superiority over the existing technologies like PIN Diodes and Field-Effect-Transistors regarding size, power, Isolation and Insertion loss, and graphically how Pull-in voltage affects on the deflection of the switch. Also this paper deals with the fabrication process of the cantilever switch.

Design optimization & fabrication of micro cantilever for switching application

This paper presents a design optimization and fabrication of Micro Cantilever which is used for switching application. The length and thickness of a cantilever beam as well as a gap space between the electrodes determines actuation voltage and should be optimized to ensure the best performance of a device. To design the cantilever switch with low actuation voltage and the current density which can be handled by the aluminium interconnects. We have optimized the design of cantilever with Taguchi method of Design of Experiments. Analysis of variance is performed to get the important design parameters from varied parameters considered. It also provides a better understanding of the key factors contributing to the performances of MEMS cantilever switch. The optimized statistical data evaluated is used to simulate the design with help of CoventorWare software. The optimized device design is implemented and electrically tested.

Low Voltage Rf Mems Capacitive Shunt Switches

Micro-electro-mechanical-systems(MEMS) switches have low resistive loss, negligible power consumption, good isolation and high power handling capability compared with semiconductor switches. Lifetime of capacitive shunt switches strongly depends on the actuation voltage so low voltage switches is necessary to enhance its performance as well as to broaden its application area. This paper presents the design and simulation of low voltage capacitive shunt MEMS switches together with its RF performance for high frequency applications. The low voltage switches are realized by lowering the spring constant of the beam using serpentine spring designs together with large capacitive area so as to achieve the good RF performance as well. The pull-in voltage is analyzed with commercial CAD finite element analysis software CoventorWare. The electromagnetic performance in terms of scattering parameters, insertion loss, and isolation are analyzed with software Ansoft HFSS10. The switches achieved insertion loss $$<$$ < 0.47 dB in on state from 2 to 40 GHz; it provided better than 25 dB isolation in off state with a capacitance ratio of 94---96. The actuation voltage as low as 1.5 V with actuation area $$110\,\times \,100\,\upmu \mathrm{m^2}$$ 110 × 100 μ m 2 along with good RF performance is reported. The design parameter optimization including selection of appropriate number of meanders and its width found to be one of the most sensitive factors affecting the spring stiffness and actuation voltage.

Design and analysis of non-uniform shaped RF MEMS switch

In this paper, we present a novel non-uniform shaped cantilever based DC contact radio frequency microelectromechanical systems (RF MEMS) switch. This switch can be employed for various wireless mobile applications in frequency range of DC-10 GHz as it shows excellent RF characteristics with low actuation voltage. The design is optimized in the terms of electrostatic actuation mechanism, which included switch beam thickness, beam gap, spring shape and materials. Also, it's optimized shape and size of contact geometry and material ensures the high reliability, high isolation and very low insertion loss. The main features of this switch are simplicity of structure, reliability of contact, excellent RF characteristics, low actuation voltage and excellent figure of merit. We investigate the proposed design with Coventorware software for electromechanical and electromagnetic analysis and, get very promising results. The paper briefly outlines the design of RF MEMS switch and also focuses on the analysis of various switching parameters.

FEM Simulation of Quartz Thickness Shear Mode Resonator for Gas Sensing Applications

The objective of this paper is to present simulation results of the Thickness Shear Mode (TSM) resonator based on quartz using finite element simulation method. 3D model of quartz resonator and simulations were completed using finite element method in CoventorWare software suite for design and simulation of MEMS devices. Different techniques for simulation of adsorption effect on selective layer were studied: influence of change in mass of the sensitive layer and influence of change in density of the sensitive layer. Analyses of resonant modes were performed for both cases and displacement profiles in selected modes were determined for the resonator under study. Impedance and phase characteristics were calculated and measured for clean sample and sample with selective layer coated. The adsorption model calculates the frequency shift in basic resonant frequency with adsorbed amount of sensed gas. The simulation results were used in design of gas sensors for dangerous substances detection.