Tan Thin Films For Dynamic Infrared Scene Generator

The infrared scene projector, as the key unit of the infrared simulation system, has been produced by many methods. As is well know, the resistor array projector was the prominent technology for its low power consumption, large temperature range, high-resolution, high duty cycle, etc. Tantalum nitride can be used in the resistor array projector because of its low temperature coefficient of resistance, relatively low thermal conductivity, high infrared emissivity, as well as changing the resistivity of thin films by changing the flow of nitrogen in the sputtering process, reusable and good operational characteristics.In this thesis TaN films were prepared by reactive magnetron sputtering. The influences of the nitrogen partial pressure, working pressure, deposition temperature, sputtering power on the microstructure and the electric properties were explored. The results show that the N2 gas partial pressure was the most influence. Rising the N2 gas partial pressure, from 1% to 20%, the deposition rate of the film decreased when the N2 gas partial pressure went up. In addition, the grain size and the properties of the films such as sheet resistance and TCR increased when the rising the N2 gas partial pressure. The phases in the as-deposited films were identified as TaN(200)when the N2 gas partial pressure was 9%. The sheet resistance increased dramatically when the N2 gas partial pressure was over 15%. With the increase of working pressure, the deposition rate of the films decresed rapidly and the sheet resistance and TCR of the films increased. With the increase of the deposition temperature the sheet resistance and TCR of the films decreased. When the deposition temperature was lower than 200℃, the X-ray diffraction patterns of the thin films show that there were no crystallization of the films and the sheet resistance and TCR of the films were great. When it was higher than 500℃, the influences of the temperature on structure of the film were no longer apparent. Relative to other parameters, the influences of sputtering power on structure of the films were small. But it was huge on the deposition rate of the films, thus affecting the film sheet resistance. In addition, with the sputtering power reduced the temperature coefficient of resistance of the films gradually become smaller. After adjustment of N2 gas partial pressure, the working pressure, deposition temperature and sputtering power, the optimized preparation parameters of TaN thin films for the resistor array projector were got. The parameters were as follow, 9% of N₂ partial pressure, 0.6Pa of working pressure, 600℃of substrate temperature, 60W of sputtering power, 30min of sputtering time. The performances of the films prepared by optimized preparation parameters were sheet resistance 48Ω/□, TCR -198ppm/℃. It could meet the reqirements of resistance array infrared scene projector.The unit of suspended membrane reisitor arrays has been producted after lithography, the wet etching of Si and SiO₂, magnetron sputtering of TaN thin films and Pt/Ti and the stipping of electrode, etc. Its apparent temperature was 308K and its rise and fall time was about 50ms,which basically meet the requirements of medium wave and long wave infrared simulation.