Research Of Ti Doped Tan Thin Film And Microwave Attenuator

For its characteristics of light weight, small size, ease of integration and high operating frequency, Microwave attenuator are widely used in modern microwave communication systems and microwave circuits. The main role of attenuators in the microwave system is to regulate the input signal without distortion. Microstrip thin film attenuator can achieve attenuation primarily through thin film material which can absorb power and converted the power to heat. As an important thin film resistive material, Ta N thin film has a very important research value. Firstly, this paper studied the performance of Ta N film material, then, a series of attenuators with different amount of attenuation were designed by using Ta N thin film as the resistance material. This paper has done the following three aspects of research work about microwave attenuator.In the aspect of materials, to achieve different ratios of Ti doped, Ti target of different areas is placed on the Ta target. In this way, the influence of different Ti-doped proportion on the resistivity and temperature coefficient of resistance(TCR) of Ta N thin film is studied. The study found that as the ratio of Ti-doped increasing, the resistivity of the thin film increases while the TCR of the thin film increases, too. When the doping ratio reached 26%, the resistivity of Ta N film has almost doubled, At the same time,TCR of thin film also increases from-45 ppm/℃ to-214 ppm/℃. The multilayer film structure is prepared by controlling the content of N2 flowed into the vacuum chamber. The multilayer film consists of metal layers and nitride layers, and the metal layer consists of Ta and Ti while the nitride layer consists of Ta N and Ti N. The study found that as the ratio of the metal layer increasing, the resistivity of the thin film decreases while the TCR of the thin film decreases, too. When the ratio of metal layers reached 67%, the TCR of thin film decreases from-166 ppm/℃ to-74 ppm/℃.In the aspect of design and simulation of attenuator, according to the idea of the multistage attenuator series, five attenuators of different attenuation are designed. All attenuators work at DC-15 GHZ, and the VSWR is below 1.25. Based on the resistive film size, the 12 d B and 13 d B attenuator are designed of 2W power load, while the 19 d B and 20 d B attenuator(two kinds) are designed of 3W power load.In the aspect of fabrication and testing of attenuator, we fabricate attenuators on the glass glazed planarized modified Be O ceramic substrate by using magnetron sputtering, vacuum evaporation and photolithography techniques; Then we fabricate the test fixture, and using vector network analyzer test the performance of the microwave attenuator and find that test results are basically consistent with the design. By loading one hour designed power on corresponding attenuator, we have measured that all attenuators’ surface maximum temperature is lower than 125℃.