Study On [Cu/MCu]_n Artificial Conductor Materials With Near-zero Eddy Current Loss

With the advent of 5G era,it is an urgent problem to be solved that the increasingly serious eddy current loss of metal interconnects at high frequencies.In order to suppress the high frequency eddy current loss,the non-magnetic metal layer and the magnetic layer can be used to the coupling of positive and negative permeability.The near-zero permeability multilayer structure can be formed to increase the skin depth significantly.However,the stress between the nonmagnetic layer and the magnetic layer will affect soft magnetic properties of the magnetic layer at high frequency.In addition,the frequency band of negative permeability in the magnetic layer is also modulated by its saturation magnetization and effective anisotropic field.Therefore,this paper focuses on how to fabricate soft magnetic films with suitable uniaxial anisotropy,saturation magnetization,low coercivity and high matching with non-magnetic layers.The main work of this paper is as follows:1.CoCu alloy thin films were prepared by electrochemical deposition.The problems of current uniformity and voltage uniformity during electrochemical deposition were investigated.The process conditions were optimized.CoCu alloy with excellent uniaxial anisotropy and small coercivity was prepared.The minimum coercivity of CoCu alloy is 22.4 Oe,and the negative permeability frequency occurs at 3 GHz.The magnetic spectra of single layer CoCu at low field FMR are measured and fitted.The negative permeability and resonance frequency appear at 1.63 GHz.On this basis,the process conditions of alternately depositing Cu/CoCu multilayers were explored.The optimum deposition voltage for alternately depositing Cu/CoCu multilayers was-0.3 V/-.1.3 V.2.NiFeCu was prepared by magnetron sputtering.In order to reduce saturation magnetization and coercivity,the process conditions of NiFeCu thin films were designed.The minimum coercivity of NiFeCu is 2.78 Oe,and the negative permeability appears above 629 MHz.On this basis,the NiFeCu/Cu/NiFeCu sandwich structure was prepared,and the dynamic high frequency magnetic parameters were further determined by low field ferromagnetic resonance testing.3.Coplanar waveguides based on Cu/CoCu and Cu/NiFeCu multilayers were designed and fabricated.It is resulted that the skin effect of Cu/CoCu multilayers as central conductors is reduced by 82 %,compared with that of copper multilayers with the same structure as central conductors.Also,skin effect is suppressed at 2 GHz-8 GHz by Coplanar waveguide with Cu/NiFeCu superlattice as central conductors.The resistance of waveguide near 5.4 GHz is 80 % lower than that of copper waveguide with the same size.