Cryogenic Pressure Sensor Calibration Facility

At present, the silicon piezoresistive pressure sensor is a mature technology in the industry, and its measurement accuracy is more rigorous in many advanced applications. Micro piezoresistive pressure sensor is fabricated by a MEMS process, and its main operational principle is that the external pressure loading causes the deflection, strain, and stress which occur on the silicon membrane. The environmental temperature, the humidity, and the pressure will reduce its performance. Moreover, the drifts of output voltage in the same temperature caused by the residual stress on the aluminum trace under thermal cycle loading also influence the performance of the piezoresistive pressure sensor. This is called the thermal hysteresis phenomenon, and the variation of output voltage is called the thermal hysteresis voltage. Among the critical issues of silicon piezoresistive pressure sensor, the hysteresis phenomenon should be deeply paid attention to obtain better sensor accuracy. For this reason, this research would like to investigate the effect of the external loading on the output voltage of a pressure sensor. Based on the process of pressure sensors, this research adopts the concept of pseudo temperature combined with a finite element method (FEM) to obtain the thermal hysteresis voltage. After several numerical analysis of thermal hysteresis voltage, the experiment is then performed to validate the simulation results. After being validated with the experimental results, the variation of thermal hysteresis voltage under a different trace layout is analyzed. Based on simulation results of a different trace layout, it is found that the trace line layout plays an important role in the thermal hysteresis performance of a pressure sensor, which indicates that the longer aluminum trace increases the hysteresis voltage. The uniform and symmetrical layout of aluminum trace can reduce the variation of resistance change and decrease the hysteresis voltage. Furthermore, the trace layout which is far away from the silicon membrane and piezoresistance is suggested to reduce the hysteresis voltage.

Sensitivity analysis of packaging effect of silicon-based piezoresistive pressure sensor

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.

Pressure measurement is a key part of many commercial and industrial systems. Piezoresistive pressure sensors are simpler to integrate with electronics, they are inherently shielded from RF noise and their response is more linear while compared to capacitive pressure sensors. And piezoresistive devices have always dominated the pressure sensor market. The analyticals that are typically used to model the diaphragm of the pressure sensor have been analysed by many researchers. To optimize the pressure sensor for parameters like linearity and sensitivity, the Finite Element Method (FEM) is incorporated. The selection of appropriate parameters of piezoresistors such as the shape and the position of the piezoresistor on the pressure sensor diaphragm, thickness of diaphragm are important. This study shows the scope of using analytical solutions and design techniques for a piezoresistive pressure sensor.

This paper describes an improvement of the membrane structure of MEMS piezoresistive(PZR) pressure sensor. Finite element method (FEM) is applied to design and optimize the property of PZR the membrane structure and piezoresistors stress analysis is performed under the rated pressure. An equation that transfers the simulation stress data into output voltage is proposed in this paper according to the Wheatstone bridge principle and piezoresisitive effect in silicon. In order to achieve better sensor performance, several kinds of output voltage curve of the membrane structure were contrasted to obtain a suitable membrane structure. The design parameters of the pressure sensor include membrane size and shape and the location of piezoresistance. After that the pressure-output characteristic, the nonlinear error of the optimization sensor and the mechanical stability were analyzed. The results confirmed that the optimization structure has good sensitivity and linearity. It is a kind of high stability, high sensitivity, and low linear error of MEMS PZR pressure sensor.

Anodic bonding between glass wafer and Si wafer are widely used for micro-electro-mechanical system (MEMS) device fabrication and packaging due to the good bonding quality. The residual stress in the bonding interface, which results from the different thermal expansion coefficients of the two wafer materials, is depended on the bonding temperature. In MEMS piezoresistive pressure sensor, the residual stress in anodic bonding, which can affect the accuracy of the device, is investigated by using the finite element method (FEM). The piezoresistive pressure sensor performance is evaluated and the residual stress effect at different temperatures is investigated in this research. The simulation results show that anodic bonding residual stress affect piezoresistive pressure sensor accuracy significantly.

Silicon piezoresistive pressure sensor uses semiconductor silicon as the force sensitive thin film, and it is produced by using the integrated technology to the lithography resistance, ion implantation, diffusion, etching and bonding on the surface offeree sensitive thin film, etc. So there are such characteristics as the high sensitivity, quick response, wide range of temperature, wide measuring range, small size, low in cost in it, etc. This kind of pressure sensor is widely used by far. However, because of adopting the semi-conductor integrated technology, the discreteness which is generated during ion implantation and diffusion makes the coefficient of the temperature of each bridge arm different. It mainly includes the thermo zero drift and the thermo sensitivity drift. Thus it makes the advantage of the silicon piezoresistive pressure sensor covered, and also bring the big difficulties to the manufacturing. So the drift compensation becomes the technical difficulty on the study and the manufacturing of the silicon piezoresistive sensor. This paper summarizes the intelligent compensation calibration algorithm for 3D polyhedron combining the practical applications of our own company. Use the pressure, temperature and the output data which is tested to build the 3D polyhedron model. To calculate the output characteristics of the compensation coefficient analog silicon piezoresistive pressure sensor and make the test output values be approximate to the target values by the method of conducting the multi-dimensional equation from the 3D polyhedron model.

A nickel–chromium (Ni–Cr) piezoresistive pressure sensor is presented, which has the advantages of low-cost and easy fabrication processes. In the designed sensor, Ni–Cr alloy (80:20 wt%), which can be fabricated using simple processes, is used as the strain-detecting material with a smaller but acceptable gauge factor. Eutectic-bonding technology, based on silver–tin (Ag–Sn) alloy, which contains 3.5 wt% Ag and has 20 µm thickness, is used as an alternative and easy bonding choice to complete the vacuum package. Normally, Ag–Sn alloy is mostly obtained by the electrochemical deposition method. However, here the Ag–Sn solder film is directly used as a bonding material. It reduces the fabrication difficulty of eutectic bonding of the proposed pressure sensor. By studying the processes of annealing of Ni–Cr fabrication and eutectic bonding with Ag–Sn, the authors complete the alloy piezoresistive atmosphere pressure sensor. Bonding quality is evaluated by inspection through the deflection of a diaphragm of silicon with more than 95% of the area successfully bonded. The pressure–voltage characteristic test results suggest a precision within 0.3% in square fitting. The temperature coefficient offset is 620 ppm/(°C free space optic (FSO)).

High reliability of piezoresistive pressure sensors by wafer to wafer direct bonding at room temperature

Flexible piezo-resistive pressure sensor based on conducting PANI on paper substrate

In this study, a variety of piezoelectric pressure transducer designs and mounting configurations were compared for measuring in-cylinder pressure on a heavy-duty single-cylinder diesel engine. A unique cylinder head design was used which allowed cylinder pressure to be measured simultaneously in two locations. In one location, various piezoelectric pressure transducers and mounting configurations were studied. In the other location, a Kistler water-cooled switching adapter with a piezoresistive pressure sensor was used. The switching adapter measured in-cylinder pressure during the low pressure portion of the cycle. During the high pressure portion of the cycle the sensor is protected from the high pressure and high temperature gases in the cylinder. Therefore, the piezoresistive sensor measured in-cylinder pressure highly accurately, without the impacts of short term thermal drift, otherwise known as thermal shock. Additionally, the piezoresistive sensor is an absolute pressure sensor which does not require a baseline or “pegging” on every engine cycle. With this measurement setup, the amount of thermal shock and induced measurement variability was accurately assessed for the piezoelectric sensors. Data analysis techniques for quantifying the accuracy of a piezoelectric cylinder pressure measurements are also presented and discussed. It was observed that all the piezoelectric transducers investigated yielded very similar results regarding compression pressure, start of combustion, peak cylinder pressure, and the overall heat release rate shape. Differences emerged when studying the impact of the transducer mounting (e.g., recessed vs. flush-mount). Recessed-mount transducers tended to yield a more accurate measurement of the cycle-to-cycle variability when compared to the baseline piezoresistive sensor. This is thought to be due to reduced levels of thermal shock, which can vary from cycle-to-cycle.

Design of piezoresistive pressure sensor for enhancing stress of MEMS cantilever

Wearable devices have developed significantly due to the use and development of various materials such as organic materials and carbon nanotubes, and the demand for wearables is also growing. The piezoresistive pressure sensor has been developed using conductive fabric coated with a simple solution coating process. The fabric has an open structure with the interconnected top and lower layers that can be utilized as pressure sensors and can detect physical movements. The piezoresistive pressure sensor has excellent resistance linearity in the low pressure to 10kPa range, as well as consistent resistance to strain up to 20% when stretched. The pressure sensor array can detect pressure-induced local deformation and will be expected to contribute considerably to the development of wearable devices with a simplified process.

Project(s): Nansen Programme executed by the Food and Agricultural Organisation of the United Nations and supported by Norwegian Agency for Development Cooperation (NORAD).Comment: Pelagic and demersal fish resources cruise; manufacture calibration were used for conductivity, temperature, pressure and oxygen sensor calibration.

The sensitivity and linearity are two extremely important performance parameters for pressure sensors. Superior sensitivity and outstanding linearity enable them to adapt to different application scenarios and accurately acquire pressure change. However, it is challenging for current piezoresistive pressure sensors to balance both of these performance aspects. This study proposes a fabric-based resistive pressure sensor with multiscale structures. The constructed resistive pressure sensor exhibits exceptional linearity exceeding 99% within a detection range of 0–1 MPa. Compared to the reported piezoresistive pressure sensors with ultrawide ranges, this sensor demonstrates higher sensitivity and a broader linear response range. In addition, this device exhibits excellent temperature tolerance. Our work will extend the application limits of sensors in fields, such as health monitoring and diagnostics, wearable devices, and human-machine interaction.