Research On The Comprehensive Simulation And Reliability Analysis Of Silicon Carbide High Temperature Pressure Sensor

With the rapid development of science and technology,the application of pressure sensors is inseparable in aerospace,oil,automobile and other fields and major engineering projects.Because the good mechanical properties and electrochemical stability of silicon carbide at high temperatures,the application of silicon carbide in pressure sensors has gradually become a research hotspot.Capacitive pressure sensors are widely used in pressure monitoring at high temperatures because of their advantages such as high sensitivity,fast dynamic response,and stable performance at high temperatures.Firstly,in this paper,the structural design,modeling and simulation analysis of the capacitive pressure sensor are carried out,and a new structure of device with the inverted conical cavity?ICCPS?is proposed.The structure has a contact mode that is superior to conventional pressure sensors,and can achieve higher capacitive sensitivity and a larger linear working range.The influence of the thickness of the pressure-sensitive film and the insulating layer on the capacitance characteristics of the sensor was studied using the control variable method.Research shows that under the external pressure of 0 to 1 MPa,the capacitance value of the ICCPS sensor can reach up to 120pF,while the maximum capacitance value of the CPS sensor is only 27pF.Moreover,the contact pressure of the ICCPS sensor is smaller,which extends the linear working range of the device by 0.2MPa.At the same time,it was also found that the capacitive sensitivity of the ICCPS sensor has also been significantly improved,up to114.1%.Secondly,the changes of the stress and strain of the sensor after being affected by temperature and pressure were deeply studied by using Ansys simulation software.The temperature varies from 25?to 600?,and the pressure varies from 0 to 0.4 MPa.The finite element method was used to simulate and analyze the physical performance of the pressure sensor under variable temperature and pressure conditions to evaluate the possible failure mechanism of the sensor in mechanical failure mode.The research shows that under the condition of constant pressure and changing temperature,the location of the maximum stress and strain of the sensor is in the metal electrode layer.The maximum strain is 6.58?10^-3?m/?m and the maximum stress is 1295.7MPa.However,the location of the maximum stress and strain on the sensor under the constant temperature changing pressure is at the junction of the SiO₂ insulating layer and the cavity.The maximum strain is 5.35?10^-4?m/?m,and the maximum stress is 227.1MPa.Finally,the process preparation of SiC capacitive pressure sensor samples and related device testing and characterization analysis were carried out.Using the Agilent B1505A device analyzer,scanning electron microscope and other equipment,a comprehensive test and analysis of the electrical characteristics and micro-morphology of the sensor sample was conducted.The research showed that the sensor's ohmic contact characteristics have deteriorated significantly after a long-term high-temperature test above 600?.After observation,it was found that the ohmic contact metal electrode changed from silver-white to black-brown,from smooth and flat to uneven.At the same time,the SiO₂ insulation layer will also be deformed or even cracked due to high temperature treatment,resulting in mechanical failure,which is consistent with the simulation results.Then using energy spectrum analyzer,X-ray diffractometer,SEM and other equipments,component analysis and cross-sectional analysis of the sensor respectively were carried out.The study found that the sensor will fail with interdiffusion and metal oxidation phenomenon at high temperature.In addition,a chemical reaction will occur between the metal and the SiC substrate to form platinum-silicon compounds,TiO₂ and other intermediate substances,which can explain the mechanism of the sensor failure mechanism.