Preparation And Study Of CoNiFe Amorphous Films And Nanogranular Films

In the blueprint of international semiconductor technology,passive integrated devices for power management are considered as an important research field to realize miniaturize system,reduce cost and improve performance in the era of"beyond Moore’s Law".For inductive on-chip power supply,as the process node of the chip is reduced to below 14 nm,the on-chip area that can be provided for the inductor becomes much smaller,and the air-coiled inductors has encoutered difficulty in maintaining high enough efficiency.Therefore,it becomes a dominant choice to introduce high permeability and low loss magnetic core to improve the inductance density and power efficiency.This thesis mainly focuses on the preparation and study of CoNiFe amorphous magnetic film.Additionally,nanogranular composite films and multilayer films have also been prepared to increase the resistivity of the films,reduce eddy current loss,and ultimately make the films more suitable for high frequency applications.The specific work is as follows:Firstly,the structure of CoNiFe films prepared by magnetron sputtering was analyzed based on differential thermal analysis and X-ray diffraction technology.It is found that the film is amorphous and has a certain temperature stability.The film with a thickness of 300 nm only crystallized until the heating temperature was raised to 700K.Meanwhile,high substrate temperature is helpful for the fcc（111）growth of the films during deposition.However,high sputtering pressure（～1Pa）facilitates the bcc（110）growth of the CoNiFe film.Secondly,the preparation process of CoNiFe film by magnetron sputtering is systematically studied.When DC magnetron sputtering is selected,the results show that excellent soft magnetic properties can be obtained at a DC power of 25W and Ar pressure of 0.13Pa.The measured saturation magnetization（4pM_S）is 18.2 k G,the easy axial coercivity(H_ce)is 4.6 Oe,the initial permeability（m_i）is>250,and the resonance frequency（f_r）is 2.68 GHz.When RF magnetron sputtering is employed,CoNiFe films with excellent soft magnetic propeirtes,4pM_S～19.3k G,H_ce～2.6Oe,m_i～449,f_r～2.6GHz and a_eff～0.0099,are obtained at a RF power of 150W and Ar pressure of 0.13 Pa.In addition,post-annealing treatment is beneficial to further improve the soft magnetic properties of the films.The resistivity of CoNiFe O layer is 448 mΩ·cm.Finally,in order to reduce high-frequency eddy current losses,CoNiFe composite nanogranular films and multilayer films were prepared and their properties were studied.The resistivity of CoNiFe-Al₂O₃ nanogranular film increases by 5-20 times,but the saturation magnetization decreases to～15k G.For CoNiFe/CoNiFe O multilayers prepared by in-situ reactive sputtering,a relatively good soft magnetic property can be obtained when the thickness ratio of magnetic layer to oxide layer is 4.4:1.The 4pM_s,H_ch,H_ce,m_i,H_k of CoNiFe/CoNiFe O/CoNiFe multilayers are 19 k G,5.5Oe,4.2Oe,231,82Oe,respectively,for an Ar pressure of 0.13Pa and P_Ar:P_O2=9:1.The resonant frequency is 2.4GHz and the effective damping factor is 0.0175.