High-frequency Soft Magnetic Thin Films And Its Electromagnetic Noise Suppression Performance Of Applied Research

With the increasing of electron device's operating frequency,it needs more advanced technology of anti-electromagnetic interference and electromagnetic compatibility(EMC) for modern electronic equipment stringently. Getting suppression of electromagnetic noise on transmission line of chip and circuits could reduce device's volume and costs while improving the whole performance. Noise suppressor using magnetic thin films, which is applied to suppress electromagnetic noise transmitting in high-frequency transmission line, is studied in this thesis. The main works are as following:Finite element analysis tool-HFSS was adopted to study the noise suppressor by placing magnetic thin film on microstrip line. The results show that the mechanism of the magnetic film noise suppressor is ferromagnetic resonance and the shift of noise suppressing frequency with film sizes is due to ferromagnetic resonance frequency(FMR) changes with demagnetizing factor.The deposition conditions of NiZn ferrite film using magnetron sputtering system were optimized. The optimum deposition conditions are as following: substrate temperature is 300℃, sputter power is 140W, sputter pressure is 0.8Pa, annealing temperature is 800℃. Further, Fe3O4 layer was prepared as underlayer for NiZn ferrite thin film. The results show that the annealing temperature decreases and imaginary value of permeability improves due to the Fe3O4 underlayer.The NiFe/IrMn multilayer thin films were grown by DC magnetron sputtering. The results show that anisotropy field Hk and exchange bias field Hex decrease gradually with the thickness of FM layers, and Hk and Hex increase rapidly with thickness of AFM layers, then become stable after the thickness over 7nm. On the hysteresis loop, two different exchange bias fields was observed, which leaded to two peaks in the permeability curves. The reason of this phenomenon maybe is that the bottom NiFe layer is pinned by monolayer of IrMn, and then results in a smaller exchange field.The coplanar waveguide was made to test the noise attenuation with magnetic films. The results show that maximum noise power attenuation of NiZn ferrite film is 3.1dB at 2.37GHz. Maximum noise suppressing frequency fmax of NiFe/IrMn multilayer is up to 6.35GHz, the maximum noise power attenuation could be 7.00dB. The results show that fmax change accordantly with FMR, which proves the mechanism of the magnetic film noise suppressor, is ferromagnetic resonance again.