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Development of preparation method and technology of alloy thin film pressure sensor

Published on: October 9, 2019 by Zetian company

In the national defense, aerospace, industrial production and automatic control systems of various countries, such as pressure measurement of launch vehicle fuel chamber, pressure monitoring of engine combustion chamber, fuel supply pressure, balance control of missile flight and downhole pressure measurement of petroleum industry, pressure sensors with high precision, high stability and resistance to harsh environment are needed, and most of them need metal elastic substrate Because of the excellent mechanical properties of metal, high temperature resistance and corrosion resistance. The key technology of piezoresistive thin film pressure sensor is the preparation process of alloy sensitive film. The preparation of alloy sensitive films with high resistance stability is the guarantee Thin film pressure sensor The key to stable performance in various harsh environments.

The function module of typical alloy film strain pressure sensor is mainly composed of elastic sensing element and conversion element. Elastic sensing element is a component that can convert the measured physical quantity into a physical quantity which can be easily transformed into electrical signal. The conversion element is a component that can directly convert the physical quantity to electrical signal. The working principle of the alloy film strain pressure sensor can be described as follows: the pressure causes the change of resistance, and the change of resistance value is converted into the change of output voltage to realize the accurate measurement of pressure. The quality of thin-film elastic element directly affects the performance and long-term stability of the sensor.

The resistance strain pressure sensor based on resistance strain effect has experienced three development stages: wire type resistance strain pressure sensor, foil type resistance strain pressure sensor and thin film resistance strain pressure sensor.

Wire type resistance strain pressure sensor is mainly made of metal wire as conversion element and pasted on sensitive element with glue. Because the metal wire of circular cross-section is not tightly combined with the deformed surface, and the terminal output line joint of resistance wire is not easy to be welded, the welding joint is easy to be damaged, so this kind of sensor has short service life, poor stability and low precision.

With the development of semiconductor manufacturing technology, especially the development of lithography technology, foil resistance strain type pressure sensor has been successfully developed. Its conversion element is foil type strain gauge, and its sensitive grid is made by photolithography and corrosion process. The foil alloy material is constantan or modified nickel chromium alloy. Due to the rectangular cross-section of foil sensitive gate, large surface area, good heat dissipation performance, uniform grid bar, small size and thin strain gauge, the temperature characteristics and accuracy of foil type resistance strain sensor have been greatly improved compared with wire type resistance strain sensor, which can meet the needs of general automatic control and measurement. However, due to the inherent defects of the adhesive itself, the mechanical properties of the adhesive become worse after being used for a certain period of time in the harsh environment such as high temperature and humidity, resulting in the poor stability of the sensor and the increase of creep and hysteresis. Therefore, the adhesive sensor can not meet the harsh environment.

 Sputtering core thin film pressure sensor

Sputtered thin film pressure sensor core

With the rapid development of modern science and technology, many industrial production and automatic control, such as pressure measurement of launch vehicle fuel chamber, balance control of missile flight and downhole pressure measurement of petroleum industry, need pressure sensors working in high temperature and corrosion-resistant environment, which urges people to develop and manufacture new pressure sensors with new technology and technological means Therefore, the metal film strain pressure sensor based on metal elastic substrate came into being. The pressure sensitive sensor is made by sputtering a thin film of SiO2 on the surface of a metal strain sensitive film, such as vacuum sputtering, and then depositing a layer of metal resistance on the surface of the pressure sensitive sensor Strain the resistance so that it is not exposed to the atmosphere, so as not to oxidize the resistance bar. If it is a metal elastic substrate, one or more layers of insulating film (such as SiO2, Si3N4, Al2O3, etc.) should be sputtered on the elastic metal substrate.

Compared with the wire type and foil type pressure sensor, the performance of the film strain type pressure sensor has been greatly improved and can adapt to the harsh environment. However, several problems need to be solved when sputtering or depositing thin films directly on metal elastic substrates: for example, the preparation of high-quality metal elastic substrates, the strong adhesion between films and substrates, and the high insulation between metal elastic substrates and thin film resistors. Zetian sensor has been engaged in the research and manufacture of pressure sensor for a long time. It has accumulated rich experience in the manufacturing process of thin film sputtering pressure purchase list. It has solved the key technology and process of thin film pressure sensor production and manufacturing. The product is stable and reliable and widely used. This article originates from Zetian sensing Please keep the reprint.