MEMS Piezoresistive Pressure Sensor Research Articles

Formulation analysis and follow-up study of multi-turn configuration for performance enhancement of MEMS piezoresistive pressure sensor utilized for low-pressure measurement applications

PurposeThe purpose of this research is to study the performance of piezoresistive pressure sensors using polysilicon as the piezoresistive material, which is typically used to measure pressure in high-temperature environments.Design/methodology/approachThe performance of this sensor is enhanced by studying the influence of multi-turn configuration at which the piezoresistors are arranged. Different configurations are studied and compared by laying down their analytical solution.FindingsThe validation of analytical results is accomplished through finite element analysis using the software COMSOL Multiphysics. The best configuration, which uses a partial triple-turn configuration, was able to achieve a sensitivity of 116.00 mV/V/MPa over a simulated pressure range of 0 to 500 KPa.Originality/valueThe literature shows the study of single-turn and double-turn meander-shaped configuration of micro-electromechanical systems piezoresistive pressure sensor but multi-turn meander-shaped configuration using a square silicon diaphragm has not been reported. Its study has reflected promising results than its counterparts based on key performance parameters such as sensitivity and linearity and are more effective to be used for automotive, aviation, biomedical and consumer electronics applications.

Prefabrication design, theoretical framework and simulation demonstration of a meander-shaped MEMS piezoresistive pressure sensor implanted on silicon substrate circular diaphragm for enhancement of key performance parameters utilized for low-pressure applications

Prefabrication design, theoretical framework and simulation demonstration of a meander-shaped MEMS piezoresistive pressure sensor implanted on silicon substrate circular diaphragm for enhancement of key performance parameters utilized for low-pressure applications

Optimizing Piezoresistive MEMS Pressure Sensor on a Double Cross Beam Silicon Diaphragm With Statistical Curve-Fitting and Optimization Techniques

Optimizing Piezoresistive MEMS Pressure Sensor on a Double Cross Beam Silicon Diaphragm With Statistical Curve-Fitting and Optimization Techniques

Enhancing Performance of a MEMS-Based Piezoresistive Pressure Sensor by Groove: Investigation of Groove Design Using Finite Element Method.

The optimal groove design of a MEMS piezoresistive pressure sensor for ultra-low pressure measurement is proposed in this work. Two designs of the local groove and one design of the annular groove are investigated. The sensitivity and linearity of the sensor are investigated due to the variations of two dimensionless geometric parameters of these grooves. The finite element method is used to determine the stress and deflection of the diaphragm in order to find the sensor performances. The sensor performances can be enhanced by creating the annular or local groove on the diaphragm with the optimal dimensionless groove depth and length. In contrast, the performances are diminished when the local groove is created on the beam at the piezoresistor. The sensitivity can be increased by increasing the dimensionless groove length and depth. However, to maintain low nonlinearity error, the annular and local grooves should be created on the top of the diaphragm. With the optimal designs of annular and local grooves, the net volume of the annular groove is four times greater than that of the local groove. Finally, the functional forms of the stress and deflection of the diaphragm are constructed for both annular and local groove cases.

Machine Learning and Swarm Optimization Algorithm in Temperature Compensation of Pressure Sensors.

The main temperature compensation method for MEMS piezoresistive pressure sensors is software compensation, which processes the sensor data using various algorithms to improve the output accuracy. However, there are few algorithms designed for sensors with specific ranges, most of which ignore the operating characteristics of the sensors themselves. In this paper, we propose three temperature compensation methods based on swarm optimization algorithms fused with machine learning for three different ranges of sensors and explore the partitioning ratio of the calibration dataset on Sensor A. The results show that different algorithms are suitable for pressure sensors of different ranges. An optimal compensation effect was achieved on Sensor A when the splitting ratio was 33.3%, where the zero-drift coefficient was 2.88 × 10-7/°C and the sensitivity temperature coefficient was 4.52 × 10-6/°C. The algorithms were compared with other algorithms in the literature to verify their superiority. The optimal segmentation ratio obtained from the experimental investigation is consistent with the sensor operating temperature interval and exhibits a strong innovation.

Quantitative analysis of MEMS piezoresistive squared diaphragm pressure sensor for biomedical applications

Now a days MEMS based for biomedical applications with high performance parameters like sensitivity and linearity are required for low pressure range.The low-pressure range (1–5 kPa) is a significant range that comprises intra-body pressures like intracranial pressure (ICP) and intraocular pressure (IOP).A lot of work on piezoresistive pressure sensor with different shapes diaphragms like squared, circular and rectangular has been carried out.In MEMS Piezoresistive Pressure sensors the most important pressure-sensitive component is the squared diaphragm. The performance of the Micro-sensor is directly determined, under uniform applied pressure with its deformation. In pressure sensor design, the accurate relationship between pressure and deformation plays a very consequence role. In this paper, squared diaphragm of silicon material is modeled and simulate using the analytical equations for a thin plate, along with the theory of small-deflection to providing quick insight regarding important parameter like stress and Deformation for the operating pressure range of 0 kPa–5 kPa. The mechanical behavior of micro-machined silicon diaphragm in terms of stress and deflection generation has been simulated.The piezoresistivity principle is used to assess the sensor's sensitivity. The mechanical change in the thin diaphragm in the form of deflection and stress is calculated and presented. In this Modeling both the analytical and simulated(FEA) results for the performance parameters such as stress, Deflection and the output voltage is computed and compared, it is found that the error between analytical and simulation results is no more than 5.6–6.5%.

Reliable before-fabrication forecasting of MEMS piezoresistive pressure sensor: mathematical modelling and numerical simulation

Reliable before-fabrication forecasting of MEMS piezoresistive pressure sensor: mathematical modelling and numerical simulation

Performance Study of MEMS Piezoresistive Pressure Sensors at Elevated Temperatures

Three types of piezoresistive pressure sensors were designed and fabricated using different process technologies incorporating standard diffused piezoresistors, and oxide isolated polysilicon or single crystal silicon piezoresistors. The performance of these sensors up to an elevated temperature of 200°C and pressure of 140 bar was investigated by measuring the variation of sensitivity, offset voltage and hysteresis. At room temperature, the diffused piezoresistor based pressure sensor demonstrated sensitivity of 0.147 mV/V/bar and it was observed to operate up to the maximum temperature of 100 °C. The oxide isolated single crystal silicon piezoresistor and polysilicon piezoresistor based pressure sensors showed sensitivities of 0.211 mV/V/bar and 0.308 mV/V/bar respectively at room temperatures. These sensors could be operated up to the measured temperature of 200 °C without any failure. All types of sensors showed decreased sensitivities with temperature. With respect to the sensitivity at room temperature, the sensor with diffused piezoresistors exhibited 13% decrease of sensitivity at 100 °C. For oxide isolated single crystal silicon or poly silicon piezoresistors, the decrease in the sensitivity at 200 °C was 19.5% and 9.0% respectively y. At elevated temperatures of 200 °C, the sensors with oxide isolated polysilicon piezoresistors demonstrated the best performance in terms of lowest decrease of sensitivity, and variation of offset voltage and hysteresis.

Development of Laser-Micromachined 4H-SiC MEMS Piezoresistive Pressure Sensors for Corrosive Environments

Making full use of the availability and excellent performance of silicon carbide (SiC) substrates, SiC-based MEMS piezoresistive pressure sensors have been extensively investigated. In this article, a femtosecond laser was adopted instead of dry plasma etching technology to realize mass fabrication of 128 bulk SiC piezoresistive pressure sensor diaphragms from half a 4H-SiC wafer. These diaphragms were completed in 2 h with an average thickness error of less than 7.5% and a surface roughness of 108 nm. The 4H-SiC sensor was characterized with a nonlinear error of 0.13% FS and a repeatability error of 1.49% FS in the pressure range of 0–5 MPa at room temperature. The tolerance to temperature was measured in high and low temperature of −50 °C–300 °C with the temperature coefficient of sensitivity (TCS) of −0.11% FS°C at −50 °C and −0.16% FS°C at 300 °C. In addition, resistance measurement of the sensor in strongly alkaline corrosive solution proved the robustness with an average daily drift of only 1.61%. This integrated solution that combines femtosecond laser technology and MEMS processing provides exciting opportunities for rapid and large-scale manufacturing of bulk SiC pressure sensors.

Multi objective design optimization of graphene piezoresistive MEMS pressure sensor using design of experiment

This paper investigates the effect of diaphragm thickness, dimensions of piezoresistors, doping profile and temperature compatibility on sensitivity and non-linearity of graphene MEMS pressure sensor. Taguchi method is used for maximizing the sensitivity and minimizing the nonlinearity of the designed pressure sensor. L27 orthogonal array is utilized for five input factors with three levels. Output voltage is obtained from simulation in COMSOL for different combinations of the input parameters as per L27 orthogonal array. It was found that diaphragm thickness and length of the sensing element shows maximum contribution in increasing the sensitivity of the pressure sensor. Similarly, interaction of diaphragm thickness with piezoresistors thickness and doping concentration shows a major contribution in reducing the non-linearity of the pressure sensor. Other factors such as operating temperature affects both sensitivity and nonlinearity of the pressure sensor with a very low contributing percentage of 0.40% and 2.16%, respectively. Pareto Analysis of variance (ANOVA) was employed to validate the predicated results of the designed pressure sensor. The result indicated that the optimum design shows a sensitivity of 4.10 mV/psi with very low non linearity of 0.1%.

Temperature Compensated Wide-Range Micro Pressure Sensor with Polyimide Anticorrosive Coating for Harsh Environment Applications

In this work, a MEMS piezoresistive micro pressure sensor (1.5 × 1.5 × 0.82 mm) is designed and fabricated with SOI-based micromachining technology and assembled using anodic bonding technology. In order to optimize the linearity and sensitivity over a wide effective pressure range (0–5 MPa) and temperature range (25–125 °C), the diaphragm thickness and the insulation of piezoresistors are precisely controlled by an optimized micromachining process. The consistency of the four piezoresistors is greatly improved by optimizing the structure of the ohmic contact pads. Furthermore, the probability of piezoresistive breakdown during anodic bonding is greatly reduced by conducting the top and bottom silicon of the SOI. At room temperature, the pressure sensor with 40 µm diaphragm demonstrates reliable linearity (0.48% F.S.) and sensitivity (33.04 mV/MPa) over a wide pressure range of 0–5.0 MPa. In addition, a polyimide protection layer is fabricated on the top surface of the sensor to prevent it from corrosion by a moist marine environment. To overcome the linearity drift due to temperature variation in practice, a digital temperature compensation system is developed for the pressure sensor, which shows a maximum error of 0.43% F.S. in a temperature range of 25–125 °C.

Design, analysis and fabrication of 4H–SiC diaphragm for piezoresistive MEMS pressure sensor

Design, analysis and fabrication of 4H–SiC diaphragm for piezoresistive MEMS pressure sensor

High-resolution current mode interface for MEMS piezoresistive pressure sensor

This work demonstrates a MEMS piezoresistive pressure sensor and its interface circuit based on a versatile current conveyor based current signal processing. To exploit the effectiveness of current mode design in VLSI, the proposed interface electronics utilizes a differential current signal and performs trans-impedance conversion through a single-ended grounded gain resistor, thus ensuring high sensitivity and linearity. The current mode approach utilizes minimal active components with just two positive current conveyors (CCII+) in a closed loop architecture, thus eliminating the need for a negative current conveyor (CCII−) or an extra CCII+ to implement the same. This approach delivers linearity and offers ease of offset balancing through external control voltages, one each for incremental and decremental cancellation. The circuit performance is investigated in simulation using AD844, which represents a functional current conveyor. Further, the proposed interface is integrated with the fabricated MEMS piezoresistive pressure sensor to obtain a sensor-electronics module. Experimental evaluation of the module reveals a sensitivity of 13.7 V/Bar for low pressure input (0-100mBar).

Impact of the diaphragm structure on the linearity and temperature sensitivity of low-pressure piezo-resistive MEMS pressure sensors

This paper presents result of a detailed simulation study aimed at optimizing the different diaphragm structures of silicon micro machined MEMS pressure sensor for operation and measurement of the low-pressure ranges(600mbar). We first show that the conventional arrangement of the Wheatstone bridge resistors realized using the “Flat diaphragms” give rise to large temperature dependence of the offset voltage which affects the sensitivity and linearity of the pressure sensors during operation in the temperatures ranging from-40°Cto+80°C, thus making the temperature compensation of the sensor output voltage rather tedious and impossible in certain instances. We further demonstrate that, this issue can be circumvented and excellent linearity with minimum dependence of the offset-voltage, sensitivity and linearity can be achieved by using “sculptured diaphragms” with optimized diaphragm dimensions. Towards this goal, in this paper, we present a set of simulation studies involving optimization of the pressure sensor diaphragm dimensions and structures with single and multiple boss structures to achieve better sensitivity, linearity, and at the same time minimize temperature drift, and to achieve better repeatability.

A high sensitive graphene piezoresistive MEMS pressure sensor by integration of rod beams in silicon diaphragm for low pressure measurement application

MEMS piezoresistive pressure sensors are most widely explored for various applications such as industrial, automotive and medical field. Each application covers a wide operating range from very low pressure to the higher pressure. In this paper a novel structure is designed by introducing the local stiffness in the diaphragm membrane for low pressure measurement. Rod beams at the diaphragm with combination of graphene piezoresistors, improves overall performance of the pressure sensor in terms of sensitivity. At higher temperature and higher pressure, a noticeable sensitivity is achieved which is compared to the previous design of graphene pressure sensor without rod beam structure. At room temperature (25 °C), sensitivity of pressure sensor with rod beam structure is 6.28 mV/psi. At 30 °C, the sensitivity is 58% higher than sensitivity of pressure sensor without rod beam structure for low-pressure specific range.

Influence of the pressure range on temperature coefficient of resistivity (TCR) for polysilicon piezoresistive MEMS pressure sensor

Sensitivity with respect to physical change of any type of sensor depends upon structure of the sensor and sensing material. If sensor is sensitive with more than single physical change (pressure or temperature etc) than sensitivity will get affected because of conflict in impact due to multiple physical parameters. Depending upon the designer’s intuition and experience, a variety of shapes of sensor had been proposed which can bear both the pressure and temperature. To understand the influence of temperature and pressure on the linearity and sensitivity, pressure sensors has been designed having 50 μm thick square diaphragm is being simulated and analyzed. The effect of pressure on Temperature Coefficient of Resistivity (TCR) of poly-silicon pressure sensor has been investigated in this paper. The stresses tempted in the piezoresistors and dislocation created in diaphragm have been studied using finite element method (FEM). The physical characteristics of sensor have been determined within the temperature range from 10 °C to 100 °C under the pressure range of 0 to 100 psi. It has been observed that TCR reduces with increasing pressure up to 30 psi, and beyond this pressure, the TCR begins to increase and thus the TCR shows the duality in nature. At 100 psi pressure, the calculated TCR for the diaphragm is found of the order of ∼7.7 × 10−3 (/°C). Thus, in conclusion, the pressure range ∼40–100 psi is recommended as the optimal range to achieve the better sensitivity. The temperature sensitivity of designed sensor has been found to be ∼0.10455 mV °C−1 while the pressure sensitivity of the proposed sensors which has been found to be 1.20051 mV psi−1. Hence, designed sensor can be used as both pressure and temperature sensing device incorporated into a single sensor.

MEMS piezoresistive pressure sensor with patterned thinning of diaphragm

PurposeThe purpose of this study is to find a new design that can increase the sensitivity of the sensor without sacrificing the linearity. A novel and very efficient method for increasing the sensitivity of MEMS pressure sensor has been proposed for the first time. Rather than perforation, we propose patterned thinning of the diaphragm so that specific regions on it are thinner. This method allows the diaphragm to deflect more in response with regard to the pressure. The best excavation depth has been calculated and a pressure sensor with an optimal pattern for thinned regions has been designed. Compared to the perforated diaphragm with the same pattern, larger output voltage is achieved for the proposed sensor. Unlike the perforations that have to be near the edges of the diaphragm, it is possible for the thin regions to be placed around the center of the diaphragm. This significantly increases the sensitivity of the sensor. In our designation, we have reached a 60 per cent thinning (of the diaphragm area) while perforations larger than 40 per cent degrade the operation of the sensor. The proposed method is applicable to other MEMS sensors and actuators and improves their ultimate performance.Design/methodology/approachInstead of perforating the diaphragm, we propose a patterned thinning scheme which improves the sensor performance.FindingsBy using thinned regions on the diaphragm rather than perforations, the sensitivity of the sensor was improved. The simulation results show that the proposed design provides larger membrane deflections and higher output voltages compared to the pressure sensors with a normal or perforated diaphragm.Originality/valueThe proposed MEMS piezoelectric pressure sensor for the first time takes advantage of thinned diaphragm with optimum pattern of thinned regions, larger outputs and larger sensitivity compared with the simple or perforated diaphragm pressure sensors.

A Novel Piezoresistive MEMS Pressure Sensors Based on Temporary Bonding Technology.

A miniature piezoresistive pressure sensor fabricated by temporary bonding technology was reported in this paper. The sensing membrane was formed on the device layer of an SOI (Silicon-On-Insulator) wafer, which was bonded to borosilicate glass (Borofloat 33, BF33) wafer for supporting before releasing with Cu-Cu bonding after boron doping and electrode patterning. The handle layer was bonded to another BF33 wafer after thinning and etching. Finally, the substrate BF33 wafer was thinned by chemical mechanical polishing (CMP) to reduce the total device thickness. The copper temporary bonding layer was removed by acid solution after dicing to release the sensing membrane. The chip area of the fabricated pressure sensor was of 1600 μm × 650 μm × 104 μm, and the size of a sensing membrane was of 100 μm × 100 μm × 2 μm. A higher sensitivity of 36 μV/(V∙kPa) in the range of 0–180 kPa was obtained. By further reducing the width, the fabricated miniature pressure sensor could be easily mounted in a medical catheter for the blood pressure measurement.

New Universal Figure of Merit for Embedded Si Piezoresistive Pressure Sensors

In this article, we are presenting a new classification methodology for high resolution membrane based MEMS piezoresistive pressure sensors embedded in Internet of Things (IoT) nodes or in body-implanted devices. This is based on a new figure of merit (FoM) that includes the four key parameters as the power consumption, the area, the noise and the sensitivity of the transducer. The proposed classification allows to directly evaluate, based on power consumption and area requirements, the ultimate limit of detection that can be reached by a proposed technology. The derivation of the proposed FoM is validated based on wide survey and comparisons of literature results. It shows that, until now, wet etching technics for membrane release still allow for reaching higher performances than reactive ion etching.

Quantitative Analysis of MEMS Piezoresistive Pressure Sensors Based on Wide Band Gap Materials

Wide band gap materials such as silicon carbide and diamond are considered more suitable compared to silicon for the fabrication of piezoresistive pressure sensors for operation at high temperatures. We have carried out extensive FEM simulation study for theoretically assessing the response of pressure sensors incorporating these wide band gap materials. Response of sensors incorporating silicon micromachined diaphragm with oxide isolated piezoresistors of diamond or silicon carbide was studied using FEM simulations. The study was further extended for sensors incorporating diaphragm as well as piezoresistors of diamond or silicon carbide. The results in both cases were compared with those obtained for a single crystal or polycrystalline piezoresistor-based silicon pressure sensor. The results presented in this paper demonstrate that among the materials studied in this work, diamond-based sensors will have the least pressure sensitivity compared to silicon carbide or silicon-based sensors. However, considering the nonlinearity of response, diamond-based sensors will have the minimum nonlinearity of pressure response compared to silicon-based pressure sensors. Hence for the same nonlinearity, it would be possible to operate the diamond-based sensors up to much higher pressures.