Study On Preparation Technology Of Thin Film Pressure Sensor

Due to its small size, light weight, low power consumption and high reliability, thin film pressure sensor has been widely used in aerospace, petrochemical, machinery, metallurgy, energy, environmental protection and other fields. At present, the focuses of domestic and foreign research about the thin film pressure sensor is based on Si and SiC substrates. The research about the thin film pressure sensor based on the alloy material is less. However, the thin film pressure sensor based on the alloy material has a very broad application prospect in the harsh environment, such as the nuclear industry, aerospace and military operations. This paper focuses on the research of the thin film pressure sensor based on the alloy material, meanwhile, the preparation process is studied in detail, including polishing treatment of the substrate, the preparation of insulating film and the preparation of the resistor film combined with micro machining technology, and the preparation technology of thin film pressure sensor is finished.First of all,two kinds of methods are used to polish the sensor substrate. The first method is to use UINIPOL-802 precision polishing machine. Specific process is that the sensor substrateis polished by different mesh sandpaper firstly, then, the polished substrateis polished by 500 nm, 250 nm diamond suspension polishing liquid and 50 nm SiO2 polishing liquid. The second method is to use Tegramin-25 precision polishing machine. The process is that the sensor substrateis polished by different mesh sandpaper firstly, and then, the polished substrateis polished by 3?m and 1?m diamond suspension polishing liquid. Compared to the two methods, the latter obtains a smoother surface, and polishing efficiency of the latter is far greater than the former.Secondly, the insulating film is studied. This paper compares a variety of insulating films, combined with the characteristics of the film and laboratory preparation conditions. Then, the SiO2 thin film is selected to make insulating film. This paper prepares insulating film by RF magnetron sputtering and plasma enhanced chemical vapor deposition(PECVD). Thenthe film prepared using PECVD is 900 nm, meanwhile, the insulation resistance is greater than500M?.Next, combined with the technical requirements of the sensor and the laboratory conditions,NiCr alloy film is selected as the sensor resistance according to the performance parameters, thin film fabrication process and lithography process. Because of the constraints of the sensor range and power waste, there are some requirements. The first one is that the film is 500nm~1?m. The second one is that the resistance is 1K?~10K?. Then, this paper studies the NiCr alloy thin film systematically. The experimental results show that resistance reduces with the increase of annealing temperature in N2. The resistance increases with the increase of annealing temperature in vacuum and air. And, with the increase of vacuum time,the resistance decreases. In the end, the NiCr film with 500 nm and 1K?~10K?is prepared by RF magnetron sputtering.Then, this paper studies the process of lithography. The lithography process is used to make resistance patterns. Usually, there are three methods to make the resistance pattern, theseare wet etching, dry etching and peeling.According to lithography process, this paper chooses peeling to make layers. The AZ5214 and AZ6112 are to be used to prepare the resistance and the protective layer. And the parameter of AZ5214 and AZ6112 is studied systematically. Finally, the resistance with line width of 30?mis successfully fabricated by selective etching process.After that, the pressure sensor is tested. For the 10 MPa range sensor, its maximum nonlinearity is 0.486%, and the sensitivity is 2.86mV/V, and the repeatability is 0.349%. For the 20 MPa range sensor, its maximum nonlinearity is 0.117%, and the sensitivity is 3.75mV/V, and the repeatability is 0.106%.For the 30 MPa range sensor, its maximum nonlinearity is 0.162%, and the sensitivity is 0.275mV/V, and the repeatability is 0.0364%.