Humidity-Induced Voltage Shift on MEMS Pressure Sensors

2003 ◽  
Vol 125 (4) ◽  
pp. 470-474 ◽  
Author(s):  
J. Albert Chiou ◽  
Steven Chen ◽  
Jinbao Jiao
Keyword(s):  
Pressure Sensor ◽  
Microelectromechanical Systems ◽  
Pressure Sensors ◽  
Anodic Bonding ◽  
Absolute Pressure ◽  
Stress Effect ◽  
Induced Voltage ◽  
Voltage Shift ◽  
Mems Pressure Sensors ◽  
Vacuum Cavity

The pressure sensor is one of the major applications of microelectromechanical systems (MEMS). An absolute pressure sensor utilizes anodic bonding to create a vacuum cavity between the silicon diaphragm and glass substrate. The manifold absolute pressure (MAP) sensing elements from a new supplier have exhibited negative voltage shifts after exposure to humidity. A hypothesis has been established that poor anodic bonding causes an angstrom-level gap between the silicon substrate and glass. Once moisture enters the gap in a vapor form and condenses as water droplets, surface tension can induce a piezoresistive stress effect that causes an unacceptable voltage shift. Finite element analyses were performed to simulate the phenomenon and the results correlated well with experimental observations.

scholarly journals A Low Temperature Drifting Acoustic Wave Pressure Sensor with an Integrated Vacuum Cavity for Absolute Pressure Sensing

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1788 ◽  
Author(s):  
Tao Wang ◽  
Zhengjie Tang ◽  
Huamao Lin ◽  
Kun Zhan ◽  
Jiang Wan ◽  
...  
Keyword(s):  
Low Temperature ◽  
Acoustic Wave ◽  
Pressure Sensor ◽  
Pressure Sensors ◽  
Silicon On Insulator ◽  
Absolute Pressure ◽  
Temperature Drift ◽  
Wave Pressure ◽  
The Absolute ◽  
Vacuum Cavity

In this paper we demonstrate a novel acoustic wave pressure sensor, based on an aluminum nitride (AlN) piezoelectric thin film. It contains an integrated vacuum cavity, which is micro-fabricated using a cavity silicon-on-insulator (SOI) wafer. This sensor can directly measure the absolute pressure without the help of an external package, and the vacuum cavity gives the sensor a very accurate reference pressure. Meanwhile, the presented pressure sensor is superior to previously reported acoustic wave pressure sensors in terms of the temperature drift. With the carefully designed dual temperature compensation structure, a very low temperature coefficient of frequency (TCF) is achieved. Experimental results show the sensor can measure the absolute pressure in the range of 0 to 0.4 MPa, while the temperature range is from 20 °C to 220 °C with a TCF of −14.4 ppm/°C. Such a TCF is only about half of that of previously reported works.

Assembly and Testing of Surface Micromachined, Piezoresistive Polysilicon Pressure Sensors

1999 ◽  
Author(s):  
Todd F. Miller ◽  
David J. Monk ◽  
Gary O’Brien ◽  
William P. Eaton ◽  
James H. Smith
Keyword(s):  
Pressure Sensor ◽  
Microelectromechanical Systems ◽  
Pressure Sensors ◽  
Single Crystal Silicon ◽  
Surface Micromachining ◽  
Process Technology ◽  
Crystal Silicon ◽  
Noise Characteristics ◽  
Testing Techniques ◽  
Piezoresistive Pressure Sensors

Abstract Surface micromachining is becoming increasingly popular for microelectromechanical systems (MEMS) and a new application for this process technology is pressure sensors. Uncompensated surface micromachined piezoresistive pressure sensors were fabricated by Sandia National Labs (SNL). Motorola packaged and tested the sensors over pressure, temperature and in a typical circuit application for noise characteristics. A brief overview of surface micromachining related to pressure sensors is described in the report along with the packaging and testing techniques used. The electrical data found is presented in a comparative manner between the surface micromachined SNL piezoresistive polysilicon pressure sensor and a bulk micromachined Motorola piezoresistive single crystal silicon pressure sensor.

Internal and external factors effect on the mobile pressure sensors’ performance

Sensor Review ◽  
2016 ◽  
Vol 36 (4) ◽  
pp. 405-413 ◽  
Author(s):  
Semih Dalgin ◽  
Ahmet Özgür Dogru
Keyword(s):  
Pressure Sensor ◽  
Mobile Applications ◽  
Pressure Sensors ◽  
External Factors ◽  
Sensor Data ◽  
High Tech ◽  
Internal Factors ◽  
Content Type ◽  
Internal And External Factors ◽  
Mems Pressure Sensors

Purpose The purpose of this study is to investigate the effect of internal and external factors on the accuracy and consistency of the data provided by mobile-embedded micro-electromechanical system (MEMS) pressure sensors based on smartphones currently in use. Design/methodology/approach For this purpose, sensor type and smartphone model have been regarded as internal factors, whereas temperature, location and usage habits have been considered as external factors. These factors have been investigated by examining data sets provided by sensors from 14 different smartphones. In this context, internal factors have been analyzed by implementing accuracy assessment processes for three different smartphone models, whereas external factors have been evaluated by analyzing the line charts which present timely pressure changes. Findings The study outlined that the sensor data at different sources have different characteristics due to the affecting parameters. Even if the pressure sensors are used under similar circumstances, data of these sensors have inconsistencies because of the sensor drift originated by internal factors. This study concluded that it was not applicable to provide a common correction coefficient for pressure sensor data of each smartphone model. Therefore, relative data (pressure differences) should be taken into consideration rather than absolute data (pressure values) when developing mobile applications using sensor data. Research limitations/implications Results of this study can be used as the guideline for developing mobile applications using MEMS pressure sensors. One of the main finding of this paper is promoting the use of relative data (pressure differences) rather than absolute data (pressure values) when developing mobile applications using smartphone-embedded sensor data. This significant result was proved by examinations applied with in the study and can be applied by future research studies. Originality/value Existing studies mostly evaluate the use of MEMS pressure sensor data obtained from limited number of smartphone models. As each smartphone model has a specific technology, factors affecting the sensor performances should be identified and analyzed precisely in terms of smartphone models for providing extensive results. In this study, five smartphone models were used fractionally. In this context, they were used for examining the common effects of the factors, and detailed accuracy assessments were applied by using two high-tech smartphones in the market.

A pressure-deformation analytical model for rectangular diaphragm of MEMS pressure sensors

2017 ◽  
Vol 31 (05) ◽  
pp. 1750046
Author(s):  
Wu Zhou ◽  
Dong Wang ◽  
Huijun Yu ◽  
Bei Peng
Keyword(s):  
Pressure Sensor ◽  
Applied Pressure ◽  
Influence Factors ◽  
Pressure Sensors ◽  
Superposition Method ◽  
Uniform Load ◽  
Pressure Sensitive ◽  
Partial Load ◽  
Mems Pressure Sensors ◽  
Measured Pressure

Rectangular diaphragm is commonly used as a pressure sensitive component in MEMS pressure sensors. Its deformation under applied pressure directly determines the performance of micro-devices, accurately acquiring the pressure–deflection relationship, therefore, plays a significant role in pressure sensor design. This paper analyzes the deflection of an isotropic rectangular diaphragm under combined effects of loads. The model is regarded as a clamped plate with full surface uniform load and partially uniform load applied on its opposite sides. The full surface uniform load stands for the external measured pressure. The partial load is used to approximate the opposite reaction of the silicon island which is planted on the diaphragm to amplify the deformation displacement, thus to improve the sensitivity of the pressure sensor. Superposition method is proposed to calculate the diaphragm deflections. This method considers separately the actions of loads applied on the simple supported plate and moments distributed on edges. Considering the boundary condition of all edges clamped, the moments are constructed to eliminate the boundary rotations caused by lateral load. The diaphragm’s deflection is computed by superposing deflections which produced by loads applied on the simple supported plate and moments distributed on edges. This method provides higher calculation accuracy than Galerkin variational method, and it is used to analyze the influence factors of the diaphragm’s deflection, includes aspect ratio, thickness and the applied force area of the diaphragm.

scholarly journals Recent Progress of Miniature MEMS Pressure Sensors

Micromachines ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 56 ◽  
Author(s):  
Peishuai Song ◽  
Zhe Ma ◽  
Jing Ma ◽  
Liangliang Yang ◽  
Jiangtao Wei ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Microelectromechanical Systems ◽  
Low Cost ◽  
Pressure Sensors ◽  
Consumer Electronics ◽  
Limited Region ◽  
Pressure Sensitive ◽  
Inner Diameter ◽  
Implantable Pressure Sensor ◽  
Mems Pressure Sensors

Miniature Microelectromechanical Systems (MEMS) pressure sensors possess various merits, such as low power consumption, being lightweight, having a small volume, accurate measurement in a space-limited region, low cost, little influence on the objects being detected. Accurate blood pressure has been frequently required for medical diagnosis. Miniature pressure sensors could directly measure the blood pressure and fluctuation in blood vessels with an inner diameter from 200 to 1000 μm. Glaucoma is a group of eye diseases usually resulting from abnormal intraocular pressure. The implantable pressure sensor for real-time inspection would keep the disease from worsening; meanwhile, these small devices could alleviate the discomfort of patients. In addition to medical applications, miniature pressure sensors have also been used in the aerospace, industrial, and consumer electronics fields. To clearly illustrate the “miniature size”, this paper focuses on miniature pressure sensors with an overall size of less than 2 mm × 2 mm or a pressure sensitive diaphragm area of less than 1 mm × 1 mm. In this paper, firstly, the working principles of several types of pressure sensors are briefly introduced. Secondly, the miniaturization with the development of the semiconductor processing technology is discussed. Thirdly, the sizes, performances, manufacturing processes, structures, and materials of small pressure sensors used in the different fields are explained in detail, especially in the medical field. Fourthly, problems encountered in the miniaturization of miniature pressure sensors are analyzed and possible solutions proposed. Finally, the probable development directions of miniature pressure sensors in the future are discussed.

A resonant high-pressure sensor based on dual cavities

2021 ◽  
Vol 31 (12) ◽  
pp. 124002
Author(s):  
Jie Yu ◽  
Yulan Lu ◽  
Deyong Chen ◽  
Junbo Wang ◽  
Jian Chen ◽  
...  
Keyword(s):  
High Pressure ◽  
Temperature Sensitivity ◽  
Pressure Sensor ◽  
Pressure Range ◽  
High Vacuum ◽  
Pressure Sensors ◽  
Anodic Bonding ◽  
Temperature Range ◽  
Pressure Sensitive ◽  
Ocean Sciences

Abstract High-pressure sensors enable expansive demands in ocean sciences, industrial controls, and oil explorations. Successful sensor realized in piezoresistive high-pressure sensors which suffer from the key issue of compromised accuracies due to serious temperature drifts. Herein, this paper presents a high accuracy resonant high-pressure sensor with the pressure range of 70 MPa. Different from conventional resonant high-pressure sensor, the developed sensor utilized a dual-resonator-cavity design to minimize temperature disturbances and improve the pressure sensitivities. Besides, four circle cavities were used to maintain a high vacuum level for resonators after anodic bonding process. In details, Dual resonators, which is parallelly placed in the tensile and compressive stresses areas of a rectangular pressure sensitive diaphragm, are separated vacuum-packaged in the parallel dual cavities. Thus, pressure under measurement bends the pressure sensitive diaphragm, producing an increased pressure sensitivity and a decreased temperature sensitivity by the differential outputs of the dual resonators. Parameterized mathematical models of the sensor were established and the parameters of the models were optimized to adjust the pressure sensitivities and the temperature sensitivities of the sensor. Simplified deep reactive ion etching was used to form the sensing structure of the sensor and only once anodic bonding was used to form vacuum packaging for the dual resonators. Experimental results confirmed that the Q values of the resonators were higher than 32 000. Besides, the temperature sensitivity of the sensor was reduced from 44 Hz °C−1 (494 ppm °C−1) to 1 Hz °C−1 (11 ppm °C−1) by the differential outputs of the dual resonators in the temperature range of −10 °C–60 °C under the pressure of 1000 kPa. In addition, the accuracy of the sensor was better than 0.02% FS within the pressure range of 110–6500 kPa and the temperature range of −10 °C–60 °C by using a polynomial algorithm.

scholarly journals Material selection for optimum design of MEMS pressure sensors

2019 ◽  
Vol 26 (9) ◽  
pp. 2751-2766
Author(s):  
Zahid Mehmood ◽  
Ibraheem Haneef ◽  
Florin Udrea
Keyword(s):  
Optimum Design ◽  
Pressure Sensor ◽  
Material Selection ◽  
Pressure Sensors ◽  
Optimum Performance ◽  
Suitable Material ◽  
Micro Scale ◽  
Selection For ◽  
Scale Properties ◽  
Mems Pressure Sensors

Abstract Choice of the most suitable material out of the universe of engineering materials available to the designers is a complex task. It often requires a compromise, involving conflicts between different design objectives. Materials selection for optimum design of a Micro-Electro-Mechanical-Systems (MEMS) pressure sensor is one such case. For optimum performance, simultaneous maximization of deflection of a MEMS pressure sensor diaphragm and maximization of its resonance frequency are two key but totally conflicting requirements. Another limitation in material selection of MEMS/Microsystems is the lack of availability of data containing accurate micro-scale properties of MEMS materials. This paper therefore, presents a material selection case study addressing these two challenges in optimum design of MEMS pressure sensors, individually as well as simultaneously, using Ashby’s method. First, data pertaining to micro-scale properties of MEMS materials has been consolidated and then the Performance and Material Indices that address the MEMS pressure sensor’s conflicting design requirements are formulated. Subsequently, by using the micro-scale materials properties data, candidate materials for optimum performance of MEMS pressure sensors have been determined. Manufacturability of pressure sensor diaphragm using the candidate materials, pointed out by this study, has been discussed with reference to the reported devices. Supported by the previous literature, our analysis re-emphasizes that silicon with 110 crystal orientation [Si (110)], which has been extensively used in a number of micro-scale devices and applications, is also a promising material for MEMS pressure sensor diaphragm. This paper hence identifies an unexplored opportunity to use Si (110) diaphragm to improve the performance of diaphragm based MEMS pressure sensors.

Thin Film Polymer Stress Measurement Using Piezoresistive Anisotropically Etched Pressure Sensors

1995 ◽  
Vol 390 ◽  
Author(s):  
David J. Monk ◽  
Mahesh Shah
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Pressure Sensor ◽  
Stress Measurement ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Film Stress ◽  
Polymeric Coating ◽  
Stress Effect ◽  
Parylene C

ABSTRACTStresses in thin polymer films have been studied for some time by using wafer bowing, bending beams, microstructure release, and laser holographic techniques. An alternative technique for measuring stresses in thin films is discussed in the following paper. Piezoresistive anisotropically etched single crystal silicon pressure sensors are sensitive not only to applied pressure, but also to applied package stress. Deposited passivation materials, like silicone gels and polyimides, have been observed to change the sensitivity of the pressure sensor. In the current work, a thin, conformal polymeric coating (parylene C) is being developed for these pressure sensors. This thin film has been observed to reduce the sensitivity of the device as a function of the film thickness and modulus and the silicon thickness and modulus. The parylene C thin films exhibit a consistent change in film stress during annealing indicating a modification to polymer crystallinity and a corresponding change in material properties. Qualitatively, the electrical output on the pressure sensor compares favorably with measurements taken using wafer bowing. Experimental DMA and TMA work has been performed to determine the modulus (7.84 × 105 psi) and CTE (39 ppm/°C at 25 °C) of the material. However, literature values of modulus (4.1 × 105 psi) have been used with finite element analysis to model the stress effect more accurately for the thin conformal coating on the pressure sensor device. These results indicate that the sensitivity of the pressure sensor will be reduced approximately quadratically as a function of the polymer coating thickness. An empirical function has been derived to estimate sensitivity loss as a function of substrate (i.e., initial diaphragm material) modulus and thickness and coating modulus and thickness.

A SOI-MEMS Piezoresistive Atmosphere Pressure Sensor

2013 ◽  
Vol 562-565 ◽  
pp. 394-397
Author(s):  
Li Dong Du ◽  
Zhan Zhao ◽  
Li Xiao ◽  
Meng Ying Zhang ◽  
Zhen Fang
Keyword(s):  
Silicon Wafer ◽  
Pressure Sensor ◽  
Strain Gauge ◽  
Pressure Sensors ◽  
Micro Electro Mechanical System ◽  
Silicon On Insulator ◽  
Anodic Bonding ◽  
Atmosphere Pressure ◽  
Piezoresistive Pressure Sensor ◽  
The Cost

In this paper, a SOI-MEMS (silicon on insulator- micro electro mechanical system) pizeoresistive atmosphere pressure sensor is presented using anodic bonding. Differently from the prevailing fabrication process of silicon piezoresistive pressure sensor: the device layer monocrystalline of SOI silicon wafer is used as the strain gauge with a simple deep etching process; and the SiO2 layer of SOI silicon wafer as the insulator between strain gauge and substrate. The whole fabrication processes of the designed sensor are very simple, and can reduce the cost of sensor. The Pressure-Voltage characteristic test results suggest a precision within 0.14% in linear fitting. It is shown that the temperature coefficient is 2718ppm/°C from the Typical temperature curve of the pressure sensors.

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