MEMS Capacitive Pressure Sensor Research Articles

Novel design of double touch plano-convex mems capacitive pressure sensor: robust design, theoretical modeling, numerical simulation and performance comparison

Novel design of double touch plano-convex mems capacitive pressure sensor: robust design, theoretical modeling, numerical simulation and performance comparison

Simulation and Analysis of Molybdenum Tungsten Impact on Capacitive MEMS Pressure Sensor

Simulation and Analysis of Molybdenum Tungsten Impact on Capacitive MEMS Pressure Sensor

Mathematical modelling of the dynamic response of an implantable enhanced capacitive glaucoma pressure sensor

Glaucoma as an eye disease influences the optic nerve, resulting in progressive vision loss and, thus, blindness. For this disease, the most important risk factor is high intraocular pressure. Therefore, it is important to accurately measure the intraocular pressure. The present work aimes to present a mathematical description of a capacitive pressure sensor based on a Micro-Electro-Mechanical-Systems (MEMS) to measure intraocular pressure (IOP). The relatively high working bias voltage of MEMS capacitive pressure sensors restricts their potential applications as implantable sensors. Hence, Polydimethylsiloxane (PDMS) is employed as a porous elastomeric substance between the deformable and fixed electrodes of the capacitor. With a low young modulus and a higher dielectric constant, it reduces the sensor's working bias voltage. The PDMS's permittivity and young modulus are a function of the porosity volume fraction based on displacement in terms of a power law with fractional power constant. The dynamic equation of the microplate's transversal motion is used in the developed model, taking mid-plane stre-tching into account along with the generated force owing to the PDMS film squeezing. To decompose the governing nonlinear equation, a weak formulation is used with appropriate basis functions, thus integrating the attained ordinary differential equations over time. The sensor response to static pressure and step-wise alteration of the applied pressure is examined by dynamic and static analysis. The results of pull-in voltage reveal that using the PDMS as a dielectric causes a considerable reduction. Additionally, the effect of the PDMS elasticity on the capacitance and displacement was assessed along with the effects of the geometrical parameters on the sensor response.

Research on a capacitive MEMS pressure sensor based on through glass via

AbstractThe paper reports the fabrication and characterization of a capacitive Microelectro Mechanical Systems pressure sensor based on through glass vias (TGV), which had a large dynamic range by operating in touch mode. The substrate with TGV offers the advantage of elimination of parasitic capacitances owing to the superior insulation property of glass. The fabrication process was introduced. In particular, anodic bonding was applied in high vacuum to realize the hermetic package to obtain large operating range and high sensitivity. The performance of the sensor with a sensitive diaphragm of 700 μm × 1400 μm was characterized in the pressure range from −80 to 180 kPa. The sensitivity was determined as 0.072 pF/kPa over the range of 160 kPa with a good linearity of 97%.

Correction: Modeling and analysis of MEMS capacitive pressure sensors with vertical comb fingers

Correction: Modeling and analysis of MEMS capacitive pressure sensors with vertical comb fingers

Characteristic Analysis of a Square Diaphragm Capacitive Pressure Sensor with Linkage Film

Capacitive pressure sensors (CPSs) have become more prevalent compared to the piezoresistive pressure sensors because they generate superior sensitivity and better linearity for the same application. Due to the innumerable use cases of the CPSs, it is becoming increasingly critical to carry out efficient analysis for their modeling. The higher sensitivity of a square diaphragm for the same side length in comparison to a circular diaphragm makes it ideal for sensor design. In this work, a complete formulation for analysis of a CPS with a square diaphragm having a linkage film has been presented. A comprehensive study of sensor parameters like capacitance, deflection of the diaphragms, capacitive and mechanical sensitivity has been formulated to aid the choice of sensor characteristics. This work also focuses on the method to determine the fundamental design parameters for optimal operation. Complex and resource-expensive methods have been used in the past for the analysis of MEMS capacitive pressure sensors. MATLAB and ANSYS have been used to compute and simulate the results.

Wafer-Level Self-Packaging Design and Fabrication of MEMS Capacitive Pressure Sensors.

This paper reports a MEMS capacitive pressure sensor (CPS) based on the operating principle of touch mode. The CPS was designed and fabricated using wafer-level self-packaged MEMS processes. The variable capacitance sensing structure was vacuum-sealed in a cavity using the Si–glass anodic bonding technique, and the embedded Al feedthrough lines at the Si–glass interface were used to realize the electrical connections between the parallel plate electrodes and the electrode pads through Al vias. The optimal design of the CPS structure was performed to trade-off the performance and reliability using finite element simulation. The CPS based on a circular-shaped diaphragm with a radius of 2000 µm and a thickness of 40 µm exhibits good comprehensive performance with a sensitivity of 52.3 pF/MPa and a nonlinearity of 2.7%FS in the pressure range of 100–500 kPa when the ambient temperature is less than 50 °C.

Square Shaped MEMS Capacitive Pressure Sensors for Biological Applications

The focus of this study is on mathematical modelling analysis and simulation of a micromechanical system based on a capacitive pressure sensor with a square diaphragm of 500 μm × 500 μm. The mechanical operation of the suggested device under the impact of a uniform pressure range employing different materials on the same arrangement is the subject of this research. The principle, design and comparative analysis of several MEMS materials are covered in this work. The deflection of the capacitive pressure sensor of roughly 0.285 μm and 30.36 pF, as well as the change in the capacitance value, are used to evaluate the device's performance. At a maximum pressure of 20 kPa at room temperature, the sensor's sensitivity is 56.24× 10-6 pF/pa, and the sensor’s response time is also reduced under static and dynamic loading circumstances. It can be seen that graphene materials have linear, stable, and repeatable properties when subjected to a uniform pressure range.

Influence of Corrugation Size and Location on Sensitivity Enhancement for MEMS-Based Pressure Sensor

In this paper, a MEMS capacitive diaphragm-based pressure sensor is investigated. The main focus of this work is to analyze the effect of the geometry and configuration on the sensitivity of a sensor as a crucial parameter in sensor design. Finite element modelling using ABAQUS software is conducted to simulate the behaviour of the diaphragm with different geometries under the same condition. Three popular geometries including square, rectangular and circular shapes with similar areas are investigated and sensitivities of 0.3, 0.24, and 0.22 µm/MPa were obtained for circular, square, and rectangular shapes respectively. Corrugated structure is added to circular diaphragm and deflection and stress analysis are provided for various positions and wave radius of the corrugated region and the best configuration based on sensitivity analysis is proposed. Simulation proved the 17.62% improvement in sensitivity by using a corrugated structure in a circular diaphragm with a small wave radius at the circumference of the circle. An increasing number of corrugated wave regions was also simulated but could not enhance the sensitivity in comparison with a one-wave corrugated structure.

Design and simulation of a MEMS MIM capacitive pressure sensor with high sensitivity in low pressure range

Abstract In this paper, the improvement of the sensitivity of a capacitive MEMS pressure sensor is investigated. The proposed spring for the sensor can increase the sensitivity. Silicon is used as the substrate and gold and aluminium nitrate are used as the diaphragm and the dielectric layer, respectively. The dimensions of the diaphragm are 150 µm × 150 µm, which is suspended by four springs. The air gap between the diaphragm and the top electrode is 1.5 µm. The proposed structure is an efficient sensor for the pressures in the range of 1–20 kPa. By using the proposed design, the sensitivity of the MEMS sensor in 18 kPa has improved to 663 (× 10−3 pF/kPa).

Design and sensitivity analysis of capacitive MEMS pressure sensor for blood pressure measurement

This paper presents the design and simulation of a MEMS based clamped capacitive pressure sensor for blood pressure measurement. Normally, Blood pressure for human beings varies in the range of 0.1–0.14 MPa. The operating range of this sensor design, modified according to the dimensions, is between 0 and 0.16 MPa. The diaphragm deflects on application of pressure which triggers a change in the capacitance between diaphragm and bottom electrode. The plates are separated by a dielectric medium ( $$ Si_{3} N_{4} $$ ). The change in capacitance, capacitive sensitivity and diaphragm deflection are observed for every design model to determine its performance. To improve the sensor performance, parameters like separation gap and diaphragm thickness are varied. The length and width of square diaphragm and overlapping area (A) are constant for all the designs. Small deflection theory ( $$ w_{\hbox{max} } = {h \mathord{\left/ {\vphantom {h 4}} \right. \kern-0pt} 4} $$ ), pull-in voltage phenomena ( $$ w_{\hbox{max} } \le {g \mathord{\left/ {\vphantom {g 4}} \right. \kern-0pt} 4} $$ ), and thin plate theory ( $$ h \cong a/10 $$ ) have been considered while designing the model. With respect to pressure, the simulation of diaphragm deflection is performed in COMSOL Multiphysics and analytical simulation for Change in capacitance and Capacitive sensitivity is performed in MATLAB.

Design and simulation of MEMS based capacitive pressure sensor for harsh environment

In this paper, we have designed and simulated a capacitive pressure sensor for harsh environment. The sensor is metal–insulator-metal type sensor in which the structure is designed using gold and the dielectric using silicon nitrate with thickness of 0.5 μm. The device achieves a linear characteristic response and high sensitivity. MIM consists of a circular clamped-edges gold membrane suspended over sealed cavity on the upper metal surface which is placed on the silicon substrate. The proposed MEMS capacitive pressure sensor is optimised and designed in COMSOL Multiphysics. The sensor illustrated with a proof mass 140 μm diameter, with air gap from 0.15 to 2 μm and pressure ranging from 200 to 1500Mpa.

New pressure sensing elements for FFR coronary catheter

The next generation FFR Coronary Catheter includes a new stable pressure sensor, AD conversion at the tip of the catheter and mount of these components on the sidewall of the catheter instead of the guide wire enabling thus to use standard guide wires. The new ultrathin capacitive MEMS pressure sensor die with corresponding readout ASIC circuit offers better accuracy, robustness and automated assembly. The measured performance values of the fabricated chips correlate well with the simulated ones indicating comprehensive understanding of the sensor operation and control of the fabrication process. The test measurements outperformed the specifications for the FFR pressure sensing.

AFM-Based Characterization Method of Capacitive MEMS Pressure Sensors for Cardiological Applications.

Current CMOS-micro-electro-mechanical systems (MEMS) fabrication technologies permit cardiological implantable devices with sensing capabilities, such as the iStents, to be developed in such a way that MEMS sensors can be monolithically integrated together with a powering/transmitting CMOS circuitry. This system on chip fabrication allows the devices to meet the crucial requirements of accuracy, reliability, low-power, and reduced size that any life-sustaining medical application imposes. In this regard, the characterization of stand-alone prototype sensors in an efficient but affordable way to verify sensor performance and to better recognize further areas of improvement is highly advisable. This work proposes a novel characterization method based on an atomic force microscope (AFM) in contact mode that permits to calculate the maximum deflection of the flexible top plate of a capacitive MEMS pressure sensor without coating, under a concentrated load applied to its center. The experimental measurements obtained with this method have allowed to verify the bending behavior of the sensor as predicted by simulation of analytical and finite element (FE) models. This validation process has been carried out on two sensor prototypes with circular and square geometries that were designed using a computer-aided design tool specially-developed for capacitive MEMS pressure sensors.

Modeling analysis and fabrication of MEMS capacitive differential pressure sensor for altimeter application

This paper proposes the modeling analysis of MEMS highly sensitive Capacitive Differential Pressure Sensor (CDPS) and also the development of a fabrication process for CDPS structures for aircraft altimeter applications. Highly sensitive CDPS structure models using circular and square sandwich polyimide diaphragm membranes, with and without center boss, were adopted, whereas other studies report on silicon diaphragms. CDPS characterization was carried out to analyze the deflection sensitivity, capacitive sensitivity, stress on diaphragm membrane and the effect of temperature on capacitive sensitivity. Simulation results of square diaphragm without center boss show better characteristics than other proposed diaphragm structures. This design yields 145.8 nm/mbar and 0.574 fF/mbar of deflection and capacitive sensitivity, respectively. The maximum stress developed on the diaphragm at maximum working pressure is less than the yield stress of polyimide material by a factor of 1.77 and capacitive sensitivity deviates at ±0.00195%/°C. From the modeling analysis, square diaphragm CDPS structure yields better characteristics and hence the fabrication process for CDPS has been developed, and its fabrication process flow verified using Intellisuit virtual fab tool.

Fabrication of Miniaturized Capacitive Pressure Sensor Using Thin Film Metallic Glass

In this paper, we proposed the process of the diaphragm for miniaturizing MEMS capacitive pressure sensor and controlling its sensitivity. We fabricated micro diaphragm using a Ru 65 Zr 30 Al 5 (at.%) thin film metallic glass (TFMG). The as-sputtered TFMG on Si substrate were annealed at 315-440°C for 5 minutes in vacuum. After annealing, micro diaphragms were fabricated by an etching Si substrate using a reactive ion etching system. Although the diaphragm without annealing had dome structure, the diaphragm annealed above 340°C formed a flat structure. The deflection of the diaphragm against applied pressure depended on the annealing temperature and decreased at higher temperatures. The pressure sensor was modeled using this diaphragms. The pressure measurement range and sensitivity were 250 Pa and 6.4×10-3 pF/Pa, respectively, for annealed at 340°C, and 1800 Pa, and 8.1 × 10-4 pF/Pa, respectively for annealed at 440°C.

Reliable before-fabrication forecasting of normal and touch mode MEMS capacitive pressure sensor: modeling and simulation

An analytical model and numerical simulation for the performance of MEMS capacitive pressure sensors in both normal and touch modes is required for expected behavior of the sensor prior to their fabrication. Obtaining such information should be based on a complete analysis of performance parameters such as deflection of diaphragm, change of capacitance when the diaphragm deflects, and sensitivity of the sensor. In the literature, limited work has been carried out on the above-stated issue; moreover, due to approximation factors of polynomials, a tolerance error cannot be overseen. Reliable before-fabrication forecasting requires exact mathematical calculation of the parameters involved. A second-order polynomial equation is calculated mathematically for key performance parameters of both modes. This eliminates the approximation factor, and an exact result can be studied, maintaining high accuracy. The elimination of approximation factors and an approach of exact results are based on a new design parameter (δ) that we propose. The design parameter gives an initial hint to the designers on how the sensor will behave once it is fabricated. The complete work is aided by extensive mathematical detailing of all the parameters involved. Next, we verified our claims using MATLAB® simulation. Since MATLAB® effectively provides the simulation theory for the design approach, more complicated finite element method is not used.

Robust Design for MEMS Sensors Based on the Fuzzy Model

First, the general theory of robust design based on fuzzy model is developed. Secondly, for a kind of capacitive MEMS pressure sensor as example, the robust design method is researched after the analyses of its structure and working principle. A mathematical model of robust design based on fuzzy model is developed. The results of robust design by programming are given.

Design and Simulation of MEMS Capacitive Pressure Sensor Array for Wide Range Pressure Measurement

Design and Simulation of MEMS Capacitive Pressure Sensor Array for Wide Range Pressure Measurement

A 33fJ/Step SAR Capacitance-to-Digital Converter Using a Chain of Inverter-Based Amplifiers

A 12 - bit energy-efficient capacitive sensor interface circuit that fully relies on capacitance-domain successive approximation (SAR) technique is presented. Analysis shows that for SAR capacitance-to-digital converter (CDC) comparator offset voltage will result in parasitic-dependent conversion errors, which necessitates using an offset cancellation technique. Based on the presented analysis, a SAR CDC that uses a chain of cascode inverter-based amplifiers with near-threshold biasing is proposed to provide robust, energy-efficient, and fast operation. A hybrid coarse-fine capacitive digital-to-analog converter (CapDAC) achieves 11.7 - bit effective resolution, and provides 83% area saving compared to a conventional binary weighted implementation. The prototype fabricated in a 0.18μm CMOS technology is experimentally verified using MEMS capacitive pressure sensor. Experimental results show an energy efficiency figure-of-merit (FoM) of 33fJ/Step which outperforms the state-of-the-art. The CDC output is insensitive to analog references; thus, a very low temperature sensitivity of 2.3ppm/°C is achieved without the need for calibration.