Of Tan Thin Film Materials And Microwave Power Film Resistor Study

Microwave power thin film resistors were widely used as an important component of RF and microwave system in radar, communications, electron countermeasure et al. In this thesis, firstly, TaN films were prepared by DC reaction magnetron sputtering. The influences of N2 partial flow, film thickness, Al doping and TaN/Al multilayer on the micro-structure and the electric properties were investigated. Secondly, the equivalent circuit model was established based on lossy transmission line theory, and the dimensions and characteristics were designed and simulated by HFSS soft ware. At last, TaN microwave power thin film resistors were prepared by DC reaction magnetron sputtering and pattern technology according to the simulation results. The main results are as follows.In the aspect of TaN thin films, the results show that the resistivity and absolute TCR of the TaN films go up gradually with the increase of the nitrogen partial flux. With increase of the nitrogen partial flux from 2 % to 6 %, the resistivity of the samples are increased from 344μΩ·cm to 1030μΩ·cm, and the absolute TCR of the sample are increased from 30ppm/℃to 750ppm/℃. However, the main crystalline phases existing in the TaN films are Ta2N when nitrogen partial flux is less than 5%, which could lead to lower absolute TCR. The main crystalline phases existing in the TaN films are TaN and Ta3N5 when nitrogen partial flux is larger than 5%, which possess higher absolute TCR. The electrical properties of TaN films are significantly affected by the thickness of films. The resistivity and absolute TCR of the TaN films are decreased slowly with the increase of the thickness of TaN films. When the thickness of films are increased from 30nm to 280nm, the resistivity of the samples are declined from 519μ?·cm to 210μ?·cm, and the absolute TCR of that are also descended from 150 ppm/℃to 30 ppm/℃. For the TaN thin film with doping Al, the resistivity and absolute TCR of the TaN films are increased moderately with the ratios of the Al/Ta area. When the ratios of Al/Ta area are increased from 0% to 30%, the resistivity of the samples are increased markedly from 250μ?·cm to 2560μ?·cm, and the absolute TCR of the samples are increased from 12 ppm/℃to 270 ppm/℃. Compared with the TaN thin films, the tuning range of resistivity is significantly increased, but the absolute TCR is not significantly deteriorated. For the TaN/Al multilayers, the resistivity and absolute TCR of the TaN films are increased gradually with the increase of nitrogen partial flux. When the nitrogen partial flux is increased from 2% to 6%, the resistivity of the samples are increased from 640μ?·cm to 1170μ?·cm, and the absolute TCR of the samples are increased from 50 ppm/℃to 350 ppm/℃. Compared with the TaN thin films, the tuning range of resistivity is wider than that of TaN tihn films.In the aspect of devices, the equivalent circuit model was established based on lossy transmission line theory. A series of microwave power resistors, such as 100W(DC～6GHz),300W(DC～1.5GHz),500W(DC～2GHz)and 800W(DC～1GHz)were designed and simulated by HFSS,. The VSWR of the designed microwave power resistors are all less than 1.2 in the range of operating frequency.TaN microwave power resistors were fabricated by DC reaction magnetron sputtering and patterned technology. The results illustrate that the absolute TCR of samples are all less than 100 ppm/℃and the surface temperature of power resistors are all lower than 120℃during the period of testing. The varying of resistance of the samples are all less than 3% a during the period of testing. The VSWR of the samples are all less than 1.2 in the range of design frequency. The measured results of the prepared samples are consistent with the design results.