Mmics Study Of Ferromagnetic Thin-film Inductors

Integrated micro-inductors is one of the important passive components to realize impedance matching, DC biasing, phase shifting and filtering in monolithic microwave integrated circuit (MMIC). It is widely used in the ampilifer, oscillator, mixer, and matching network unit circuits. The integration of magnetic materials into micro- inductors can not only increase the inductance but also reduce magnetic loss of inductors. It is a promissing way to realize high performance integrated micro-inductors through integration of magnetic materials into inductors. In this thesis, the performance and fabrication processes of NiFe-SiOx magnetic thin films for high frequency have been studied. Based on these studies, the MMIC micro-inductors with NiFe-SiOx thin films were fabricated by using standard MMIC integrated technology. The experimental results show that the integration of magnetic materials into inductors can enhance the performance of MMIC micro-inductors effectively.The thesis is organized as follows: firstly, we use the TRL calibration method to solve the well-known problem that the magnetic materials with a magnetic bias can not be simulated in Ansoft HFSS, and use this method to simulate the micro-inductors with magnetic films. The structure and layout of MMIC micro-inductors with magnetic thin films were designed based on the simulation results.Then, two types of NiFe-SiOx magnetic thin film were fabricated by magnetron sputtering: sandwich-type multilayer film ( ????NiFe =40%) and composite film (????NiFe =60%), annealed by conventional furnace anneal. The test result show that: the surface shape and magnetic performance of the sandwich-type multilayer film were better than the composite film.Micro-inductors with magnetic films were fabricated by standard MMIC processes on GaAs and GaN substrates. According to the specific need of our processes, we improved and optimized the lithography and lift-off processes. All the processes are compatible with standard MMIC processes.The microwave performance of the inductors with magnetic thin films was tested by Vector Network Analyzer. The results show that the magnetic thin films enhance the inductance of the micro-inductors effectively. However, because of the eddy current loss in high-frequency, the quality factor(Q) of all the inductors with magnetic thin films are lower than the air-core inductors. The variation of the performance of the inductors with the physical parameters of the coil and magnetic thin films is consistent with the simulation results. In lower frequency band (1GHz~6GHz), microwave absorption occurs in the inductors with sandwich-type multilayer magnetic films. The resonance frequency is decreased with the increase of the volume of the magnetic film.Finally, based on the characteriatics of two types of NiFe-SiOx magnetic films and the test result, ADS fitting optimization method was used to improve the existing lumped parameter equivalent circuit model of the inductors with magnetic thin films. The lumped parameter equivalent circuit model was obtained which is in better agreement with the measurement of our inductors.