Research Of Preparation And Technology Of Silicon- Based Alumina Humidity Sensor

Al₂O₃ capacitive dew point meter,as a common equipment in micro-moisture detection,can measure dew point temperature-100?.It is often used in semiconductor preparation process,gas manufacturing process,SF6 gas detection in power industry,high-altitude atmospheric analysis and other fields,and has a wide range of industry needs and applications.At present,there is no stable manufacturing capability of humidity sensor,which is the key component of Al₂O₃ capacitive dew point meter in China.It basically depends on foreign imports,and the imported components are expensive.At present,the commonly used Al₂O₃ capacitive dew point meter has a big drift due to the defects of anodic oxidation manufacturing process,and it needs to be calibrated every six months.Moreover,with the increasing demand for integrated measurement of humidity,temperature and pressure,Al₂O₃ capacitive sensors need to be integrated.In order to meet the requirement of multi-functional integration and long-term stability of common dew point instruments,porous Al₂O₃ humidity-sensitive thin films with high stability were prepared by micro-arc oxidation process on aluminium and silicon substrates.The structures of Al-based and Si-based humidity-sensitive thin films were designed according to the structure of porous Al₂O₃ thin films.The equivalent circuit of humidity sensor is established and the impedance of the equivalent circuit is analyzed.According to the principle of micro-arc oxidation process,the complete oxidation preparation process of Al-based and Si-based humidity-sensitive films was designed and developed,and the micro-arc oxidation preparation platform was built according to the preparation process design.The crystal structure and surface morphology of porous Al₂O₃ thin films were analyzed by X-ray diffraction and scanning electron microscopy.The results show that increasing oxidation time and oxidation current in micro-arc oxidation process can increase the content of crystalline phase of alpha-Al₂O₃ in the thin films,increase the diameter of surface voids and the number of surface cracks,and the mass ratio and temperature of electrolyte affect the crystalline phase and surface morphology of Al₂O₃ thin films.Appearance has little effect.On the basis of the principle of humidity generator,a set of humidity-sensitive performance test platform was designed and constructed.The humidity-sensitive characteristics of Al-based and Si-based sensors were tested and analyzed,and the effects of micro-arc oxidation process parameters on the humidity-sensitive characteristics were explored.The results show that the sensitivity of Al₂O₃ humidity sensor decreases with the increase of oxidation current and time,but the response speed of humidity sensor increases first and then decreases.Finally,a silicon-based humidity sensor with good sensitivity and response speed was prepared,which accumulated experience for the follow-up study of multi-functional integration of humidity sensors.