The Research Based On TaN Thin Film

The integration and minimization of microwave loads and components used in the fields such as satellite network and radar system has always been the main direction of the research on microwave communication at home and abroad. Because of the brilliant physical and chemical characters,Ta N thin film has become one of the most hottest RF resistance and microwave load material uesd in the next generation. More and more researchers try to realize the the integration of microwave devices through photolithography process and the deposited film technology. Based on this background, this paper studied the theoretical design and preparation technology of tantalum nitride thin film and the integrated devices on account of TaN on the nickel-zinc ferrite substrate. It has concluded the relationship between the technological parameter and the various performance of TaN thin films. Microwave loads which could work in the high-frequency situation has been made out by TaN thin film after the theoretical design and the software simulation. AlN thin film has been made and firstly used to solve the surface properties and heat dispersion of the substrate to improve the power performance of the TaN thin film microwave loads. Micro-strip integration isolator has been simulated and made in the end.Firstly, reliable and excellent TaN thin film was prepared on Ni-Zn ferrite substrate by DC reactive magnetron sputtering technique. By changing the conditions such as sputtering pressure, sputtering time, nitrogen partial pressure, distance between target and substrate and the sputtering power, experiments studied the phase structure, sheet resistance, temperature coefficient of resistance(TCR) and other parameters of TaN thin film. After many systematic experiment, it concluded the rule and formulate the appropriate technological parameter. The backing vacuum degree was between 3.42×10-5and 5.65×10-5Pa, the sputtering pressure was between 0.61 and 0.65 Pa, the sputtering argon flow was 50 sccm, the nitrogen flow was 3sccm, the sputtering time was 1200 s,the distance was 7cm, the sputtering power was 50 W.The TaN thin film prepared by this condition had the sheet resistance of 46-52Ω/sq, the temperature coefficient of resistance(TCR) was 48-62ppm/℃, and the thickness was between 293 nm and 315 nm.Secondly, 2mm×2mm×0.5mm TaN thin film microwave loads model working in 20-40 GHz had been designed, simulated and optimized through HFSS software. The simulation result shows that the voltage standing wave ratio(VSWR)was less than 1.3, return loss(S11) was less than-20 dB, real part of the Z parameter was between 41 and 54Ω. Through photolithography process and the deposited film technology, TaN thin film microwave loads were made, after testing,the actual voltage standing wave ratio(VSWR)was less than 1.5, return loss(S11) was less than-13 dB, impedance was between 40-70Ω, power density was just 0.91W/mm2.Thirdly, as a result of the bad surface character and internal structure of the nickel-zinc ferrite substrate, the power density always fall of the practical applications. Through medium frequency magnetron reactive sputtering, 1.5μm AlN thin film was made between the substrate and the TaN thin film microwave loads and improved the surface properties and heat dispersion of the substrate, remarkably improved the power performance which could attain 3.76 W/mm2.At last, based on the learning of micro-strip circulator field theory and the Y-junction circulator design method, designed and simulated micro-strip circulator and integrated isolators whose one port was contacted by the TaN thin film microwave load by HFSS software, and made and tested the isolators. Between 20-30 GHz frequency simulation, circulator’s return loss(S11) was less than-15 dB, insertion loss(S12) was about-1dB, isolation(S21) was less than-14 dB.Between 10-14 GHz frequency simulation, isolators’ S11 was less than-14 dB, S12 was about-1dB, S21 was less than-15dB; based on the theoretical design and guided by the simulation results, through many times photolithography process and the deposited multilayer film technology, isolators were made and tested,,the actual isolators’ S11 was less than-10.5dB,S12 was more than-3dB,S21 was less than-10 dB,almost close to the results of simulation.