Research status and development trend of the hotte

Research status and development trend of pressure sensors

Abstract: This paper discusses the research history, status and development trend of pressure sensors, and provides some references for the technical developers of sensors

key words: pressure sensor; present situation; Trend

sensor technology is one of the important technologies of modern measurement and automation systems. Almost every technology can not be separated from sensors, from the development of the universe to the exploration of the seabed, from the control of production process to modern civilized life. Therefore, many countries attach great importance to the development of sensor technology. For example, Japan lists sensor technology as one of the six core technologies (computer, communication, laser, semiconductor, superconductor and sensor). Among all kinds of sensors, pressure sensors have the advantages of small volume, light weight, high sensitivity, stability and reliability, low cost and easy integration. They can be widely used for the measurement and control of pressure, height, acceleration, liquid flow, flow rate, liquid level and pressure. In addition, it is also widely used in water conservancy, geology, meteorology, chemical industry, medical and health care, etc. Because this technology is a combination of plane technology and three-dimensional processing, and it is easy to integrate, it can be used to make sphygmomanometers, anemometers, water velocimeters, pressure gauges, electronic scales and automatic alarm devices. Pressure sensor has become the most mature, stable and cost-effective sensor among all kinds of sensors. Therefore, technicians engaged in modern measurement and automatic control must understand and be familiar with the research status and development trend of pressure sensors at home and abroad

1 development history of pressure sensor

modern pressure sensor is marked by the invention of semiconductor sensor, and the development of semiconductor sensor can be divided into four stages [1]:

(1) invention stage (1945-1960): this stage is mainly marked by the invention of bipolar transistor in 1947. Since then, this characteristic of semiconductor materials has been widely used. C.S. Smith and 1945 found the piezoresistive effect of silicon and germanium [2], that is, when an external force acts on the semiconductor material, its resistance will change significantly. The pressure sensor made according to this principle is to stick the strain resistor on the metal film, that is, convert the force signal into an electrical signal for measurement. The minimum size at this stage is about 1cm

(2) technical development stage (1960-1970): with the development of silicon diffusion technology, technicians choose the appropriate crystal direction on the (001) or (110) crystal surface of silicon, directly diffuse the strain resistance on the crystal surface, and then process it into a concave shape on the back to form a thin silicon elastic diaphragm, which is called silicon cup [3]. This kind of silicon cup sensor has the advantages of small volume, light weight, high sensitivity, good stability, low cost and easy integration. It realizes metal silicon eutectic and provides the possibility for commercial development

(3) commercial integrated processing stage (1970-1980): Based on the diffusion theory of silicon cup, the anisotropic corrosion technology of silicon is applied. The processing technology of diffused silicon sensor is mainly based on various anisotropic corrosion technologies of silicon, and has developed into a silicon anisotropic processing technology that can automatically control the thickness of silicon film [4], mainly including V-groove method, concentrated boron automatic suspension method, anodic oxidation automatic suspension method and microcomputer controlled automatic suspension method. Because it can be corroded on multiple surfaces at the same time, thousands of silicon pressure films can be produced at the same time, realizing the integrated factory processing mode and further reducing the cost

(4) micromachining stage (1980 present): the emergence of Nanotechnology at the end of the last century makes micromachining possible

through the micromachining process, the structural pressure sensor can be processed by computer control, and its linearity can be controlled within the range of microns. Using this technology, micro grooves, strips and films can be processed and etched, making the pressure sensor enter the micron stage

2 research status of pressure sensors at home and abroad

from a worldwide perspective, the development trend of pressure sensors mainly includes the following directions

2. 1 optical fiber pressure sensor [5]

this is a kind of sensor with more research results, but not too many are put into the actual field. Its working principle is to use the characteristics related to the deformation of the sensitive element under pressure and the intensity of reflected light. A silicon optical fiber baffle is sandwiched in the middle of the diaphragm structure composed of silicon frame and gold chromium film. Under pressure, the intensity of light will change when it passes through the baffle. By detecting this small change, we can measure the pressure. This kind of sensor has been used in clinical medicine to measure the pressure in the balloon of dilated coronary artery catheter. It can be predicted that this pressure sensor will have a good development prospect in microsurgery. At the same time, optical fiber sensors are also developing rapidly in processing and health care

2. 2 capacitive vacuum pressure sensor [6]

the capacitive pressure sensor of E + H company is composed of a substrate and a thickness of 0 8～2. 8mm aluminum oxide (Al2O3), between which a self fusion welding ring is brazed together. The ring has the function of isolation, does not need temperature compensation, and can maintain the reliability and lasting accuracy of long-term measurement. The measurement method adopts the capacitance principle. One capacitance CP on the substrate is located in the center of the diaphragm with the largest displacement, while the other reference capacitance Cr is located at the edge of the diaphragm. Because the edge is difficult to produce displacement, the capacitance value does not change. The change of CP is related to the change of applied pressure, and the relationship between displacement and pressure of the diaphragm is linear. In case of overload, the diaphragm will not be damaged when stuck on the substrate. When there is no load, it will immediately return to its original position without any lag. The overload can reach 100%, and even if it is damaged, it will not leak any polluting medium. Therefore, it has broad application prospects

2. 3 high temperature pressure sensor

the emergence of a new semiconductor material silicon carbide (SIC) makes it possible to make a single crystal high temperature sensor. Rober. S. Okojie reported a new kind of α (6h) sic pressure sensor The experimental results show that when the input voltage is 5V, the measured pressure is 6 Under the condition of 9Mpa, the full-scale output at 23500 ℃ is 44. The scheme is proposed 66～20. 03mv, full scale linearity is 20 17%, hysteresis is 0 17 %。 After operating at 500 ℃ for 10h, the performance is basically unchanged, and the strain temperature coefficient (TCGF) at 100 ℃ and 500 ℃ are 20 19%/℃ and - 0 11 %/℃。 The main advantages of this kind of sensor are that the leakage current of PN junction is very small, there is no heat matching problem, and the temperature rise does not produce plastic deformation, so it can be processed in batches. Ziermann, Rene reported the use of single crystal n-type β- The pressure sensor made of SiC material has a working temperature of 573K and is radiation resistant. At room temperature, the sensitivity of this pressure sensor is 20 2muV/VKPa。

2. 4 silicon micromachining sensors

today, with the gradual improvement of micromachining technology, silicon micromachining sensors are more and more used in the automotive industry. As the volume of micro mechanical sensors becomes smaller and smaller, the linear 53 coagulated Solvay super performance polymer shows a very high PV value of up to 4million psi*ft/min (140mpa*m/s) in harsh environments. The earth block can reach 1 ~ 2mm, and can be placed in important organs of the human body for data collection. Hachol ,Andrzej ; Dziuban, Jan bochenek reported a tonometer that can be used to measure the eyeball, with a diaphragm diameter of 1mm. When the intraocular pressure is 60mmhg, the static output is 40mv, and the sensitivity coefficient is relatively high

2. 5 pressure sensor with self-test function

in order to reduce the cost of debugging and operation, Dirk de bruyker et al. Reported a piezoresistive and capacitive dual element sensor with self-test function. Its self-test function is based on the principle of thermal drive. The size of the sensor is 1 2mm × 3mm × 0.5mm, suitable for biomedical field [7]

2. 6 multi dimensional force sensor

the research and application of six dimensional force sensor is the hot spot of multi-dimensional force sensor research. At present, only a few countries such as the United States and Japan can produce it internationally. On the basis of tracking the development of foreign countries, Beijing University of technology has groundbreaking developed a soft optical array tactile with piezoelectric layer. The array density is 2438tactels/cm2, the force is sensitive 1g, and the structure is flexible. It can grasp and recognize eggs and steel balls. It has been used for robot sorting articles [8]

3 development trend of pressure sensors

nowadays, the research field of pressure sensors in various countries in the world is very extensive, which has almost penetrated all walks of life, but it can be summarized into the following trends:

(1) miniaturization. At present, the market has a growing demand for small pressure sensors. This kind of small sensors can work in extremely harsh environments, require little maintenance and repair, and have little impact on the surrounding environment, It can be placed in various important organs of the human body to collect data without affecting people's normal life. For example, the sensor with a range of 2 ~ 500PSI produced by American entran company has a diameter of only 1 27mm, which can be placed in the blood vessels of the human body without having a great impact on the circulation of blood

(2) integrated pressure sensors have been increasingly integrated with other measurement sensors to form measurement and control systems. The integrated system can improve the operation speed and efficiency in process control and factory automation

(3) intellectualization due to the emergence of integration, some microprocessors can be added to the integrated circuit, so that the sensor has the functions of automatic compensation, communication, self diagnosis, logic judgment and so on

(4) another development trend of extensive pressure sensors is that they are expanding from the machinery industry to other fields, such as automotive components, medical instruments and energy and environmental control systems

(5) the design and manufacture of standardized sensors have formed a certain industry standard. Such as ISO international quality system; American ANSI, ASTM standards, Russian Г OCT, Japanese J is standard

4 Conclusion

with the progress of silicon, micromachining technology, VLSI technology and material preparation and characteristics research, it is possible for pressure sensors to be used in the mass production of optical fiber sensors, the application of high temperature silicon piezoresistive and piezoelectric junction sensors. Pressure sensors have a wide range of application prospects in biomedicine, micro machinery and other fields

References:

[1] S. M. sze Semiconductor sensor , 1994 chapter IvppIV.

[2 ] C. S. Smith , piezoresistive effect in germanium and silicon phys.

[3] Feng Jingxing New technology of electrostatic sealing and silicon cup corrosion [j] Journal of Fuzhou University, 1994

[4 ] Desnical UV. SanticB. Trap - induced photoconductivity in semi - insulating gallium arsenide. 1989.

[5] white Shaohong Development of optical fiber pressure sensor [j] Industrial instrumentation and automation, 1990

[6 ] Yuelin Wang et al , The structures for electrostatic servro capacitive vacuum sensor ,sensors and actuators A 1998.

[7 ] Dirk De Bruyker et al , A combined piezoresitive pressure sensor and function based on thermal actuation sensors A ,1998.

[8] Zhang Weixin, et al Semiconductor sensor [m] Tianjin: Tianjin University Press, 1990

introduction of the author: Zhang Xin, male, born in 1981, is a master's student of Shandong Agricultural University in 2002. His research direction is intelligent water-saving agricultural control. (end)