be based on SiC （ Silicon Carbide ）The high temperature pressure sensor is gradually becoming the mainstream research direction in the field of high temperature sensor, SiC It has been widely used in the development of high temperature sensors because of its excellent high temperature mechanical properties, easy processing and the advantages of semiconductor materials. Based on different principles SiC The performance of the sensor is also improving, which can meet the requirements of ultra-high temperature（ <800 ℃ ）Pressure measurement requirements in most high temperature environments. With the increasing use temperature of ohmic contact, SiC The continuous improvement of optical fiber performance, SiC The measurement in ultra-high temperature environment also has a broad application prospect. At present, SiC High temperature pressure sensors are mainly used in the combustion chamber of power equipment such as aviation and aerospace engines, rocket engines, aeroengines, heavy gas turbines, coal-fired gas boilers, etc. At home, there is production SiC The production line of high temperature pressure sensor has been used to measure the high temperature pressure of oil well. Abroad, there are already SiC High temperature pressure sensor, high pressure is more mature, micro pressure is also available for sale. Can work in six hundred About degrees, NASA Invest in cooperative R & D. High temperature pressure sensor More mature materials are based on SOI and SiC 。 According to research SOI stay five hundred It will undergo plastic deformation. and SiC Can be used at higher temperatures.
be based on SiC As the third generation direct transition wide band gap semiconductor material, silicon carbide has excellent radiation resistance, thermal performance and corrosion resistance. Sic It has many crystal forms and is commonly used in the development of high temperature pressure sensors a Type 3C -SiC and B Type 4H 、 6H-SiC In which B-SiC stay one thousand and six hundred ℃ It has a wide application prospect in the preparation of high temperature sensors. At present, SiC Dry etching, ohmic contact preparation and SiC-SiC Wafer level bonding and other micromachining technologies have been basically mature SiC The high-temperature sensor has become a hot research direction of high-temperature sensor. be based on SiC The high-temperature pressure sensors mainly include piezoresistive type and capacitive type.
SiC Piezoresistive high temperature pressure sensor
At present, the pressure resistance sensor is simple and reliable SiC The research hotspot of pressure sensor is also one of the most fruitful projects. one thousand nine hundred and ninety-seven At the Technical University of Berlin, Germany Zeirmann Waiting for you SOI There is a layer on the structure 3C -SiC Film, and use RIE The piezoresistor is etched to realize the pressure measurement and the working temperature is up to four hundred and fifty ℃ 。 NASAGlenn The research center in piezoresistive pressure sensor research carried out more in-depth, the center is the first to achieve the full range SiC Structure of the pressure-sensitive chip. Pressure sensitive structure 6H-SiC As the substrate, it is formed by homoepitaxial doping and dry etching technology PN Junction and piezoresistive structure for reuse Ti/TaSi/Pt Ohmic contact is realized in the film system. The highest working temperature of the sensor can be achieved seven hundred and fifty ℃ 。 limit SiC There are two factors affecting the working temperature of piezoresistive high temperature sensor: ① epitaxy at high temperature 6H-SiC The piezoresistive effect of the film is degraded, Glenn Data from the center show that, 6H-SiC The piezoresistive coefficient of the film at room temperature is 0 thirty , and in the six hundred ℃ Time drops to 10-15 ；② SiC Temperature limits for use with ohmic contacts, Ti/TaSi/Pt 、 Ta/Ni/Pt The long-term service temperature of the equal ohmic contact film system is not higher than eight hundred ℃ 。
SiC Capacitive pressure sensor
The capacitive pressure sensor has the characteristics of high sensitivity, fast dynamic response and high temperature stability. Western Reserve University of the United States has carried out in-depth research on capacitive high-temperature pressure sensor, two thousand and four The school's Young
Darrin J And so on APCVD Deposition on silicon substrate 3C -SiC The structure of the pressure sensing unit is shown in the figure. Because the pressure sensing film is thin, the center of the membrane contacts with the bottom when the sensor works. The maximum operating temperature of the sensor can reach four hundred ℃ Is the sensitivity at this temperature 7.7fF/torr 。 two thousand and eight The school's Chen Li A new comprehensive method is proposed SiC Capacitive pressure sensor of structure. In this program Chen Using low temperature oxides LTO （ Low-temperature Oxidation ）As a sacrificial layer and sealing material, the maximum working temperature of the sensor is five hundred and seventy-four ℃ 。 In addition, France LETI The Institute has also carried out SiC Research on capacitive high temperature pressure sensor, main technical indicators: working temperature higher than six hundred ℃ , range 65kPa-145kPa Sensitivity 1pF/100kPa , nonlinear <1%FS , precision <1%FS25 。 Yin Yugang and others of Beijing Telemetry Technology Research Institute have done outstanding work 4H-SiC The whole of SiC Capacitive high temperature micro pressure sensor, working temperature can reach six hundred ℃ , realized 0~3kPa The accuracy of the whole temperature range is up to 3% , reaching the domestic leading level. Similar to piezoresistive high temperature pressure sensor, the working temperature of capacitive high temperature pressure sensor is also limited by SiC The working temperature of ohmic contact and the increase of insulation leakage current at high temperature will reduce the accuracy of capacitance measurement.
SiC The key technologies of high temperature pressure sensor are as follows:
one Electrochemical corrosion
two Deep reactive ion etching
SiC At present, there are some problems in high temperature pressure sensor
one The etching depth is difficult to control.
two It is difficult to produce patterns due to the influence of microchannels.
three Lead free packaging process
one 、 SiC The substrate is commercially available.
two Electrochemical etching and deep reactive ion etching were combined to control the etching depth.
three High conductivity metal and glass powder are used as the transition between electrode and outer lead. This article originates from Zetian sensing Please keep the source.