A Research Of Integrated Magnetic Thin Films And Filter In GHz Frequency Band

The conduction mode of electromagnetic interference(EMI)in integrated circuits and other electronic devices has become one of the current international hot issues.The most effective way of eliminating the electromagnetic interference in integrated circuits and transistors and other active devices and systems is to develop magnetic integrated thin film EMI filter.The primary task of integrating miniaturized thin-film EMI filter is to increase the cut-off frequency fr to GHz band,at the same time,make the magnetic film maintain excellent soft magnetic properties and high frequency performance.As the material is the basis of the device,high performance,wide frequency band and low loss of the soft magnetic film are keys to achieving high performance for integrated magnetic core devices.For the integrated anti-EMI filter applied to GHz range,the magnetic thin film must meet the application requirements of high frequency range,that is to say,its cut-off frequency fr must reach GHz band with high permeability and low loss tangent tg?.The electromagnetic properties and high frequency performance of the magnetic film must be adjustable depending on application requirements.Based on the explicit performance requirements of soft magnetic thin films,CoNbZr soft magnetic thin films are used for study of magnetic core in this paper,then optimize and design coplanar waveguide,and then integrated fabricate the GHz filter,which can be applied to the suppression of electromagnetic interference.Firstly,CoNbZr thin films are deposited on silicon substrate by rf magnetron sputtering.We have investigated the effects of film thickness,sputtering power,sputtering pressure and sputtering angle on the high frequency performance and magnetic properties of films.It is found that films have the best performance at the power of 250 W,sputtering pressure of 0.4Pa,and the thickness of 140 nm.The easy axis coercivity(Hce)is 14 Oe,in-plane uniaxial anisotropy field(Hk)is 98 Oe,the saturation magnetization(4?Ms)is 15.9 KGs,the natural resonance frequency(fr)is3.5 GHz.Moreover,with the increase of oblique angle,Hk and fr of the film tend to increase,but at the same time it lead to an increase of Hce and a decrease of permeability.During this process,the microcosmic mechanism and physicalmechanism of the influence of process parameters on the magnetic properties of the films have been analyzed.Then,the size of coplanar waveguide(CPW)was calculated by high-frequency structure simulator(HFSS),and its fabrication was completed by traditional electroplating process.Its transmission loss(S21)is less than 0.4 dB within the test range of 300 kHz to 20 GHz,which satisfies the impedance matching condition.In addition,A filter were designed by integrating the CoNbZr thin film with CPW.by exerting a magnetic field with a certain angle to the magnetic film plane,A multi-frequency narrowband band-stop filter was obtained in 10GHz-40 GHz range.Finally,the GHz magnetic core integrated filter for anti-EMI is fabricated by microelectronic lithography technology.The CoNbZr thin film are integrated on the CPW.noise signal are absorbed and attenuated through magnetic film.Without bias magnetic field,the device has an absorption resonance peak at 3.75 GHz and the magnitude of signal attenuation at the peak center is-8.3 dB.Meanwhile,the loss mechanism of the device is analyzed,the ferromagnetic resonance loss of the magnetic thin film is considered to be the main factor.