Study Of The Properties Of Nanoscale Thin Films Sputtered By High Purity Ferromagnetic Metal Target

In recent years,semiconductor technology and various advanced electronic components have been developed rapidly.Ferromagnetic rare and precious metals and their alloy sputtering targets have become a new material that supports the manufacture of advanced components such as integrated circuits,discrete devices,and memory chips,which has broad market prospects.However,ferromagnetic materials usually have unique electrical and magnetic properties,the production of high-purity metal targets is very difficult,and related products are almost exclusively monopolized by Western companies.Aiming at the current deficiencies in the processing and manufacturing of ultra-high-purity ferromagnetic metal targets in our country,in this Ph.D dissertation,we carry out relative research.On the one hand,we carry out research on the correlation between target materials and sputtering thin film performance to provide theoretical guidance for the research and development of high-quality and high-performance target materials.Generally,it has been demonstrated that the properties of thin films are usually affected by thin film thickness,strain,defects,the interface roughness,etc.On the other hand,different nano-magnetic multilayer films are prepared by magnetron sputtering.Through introducing insert interface layer,introducing surfactant,appropriate covering layer,and optimizing the temperature of annealing treatment to study the influence of the interfacial electronic structures on the film performance and reveal the related mechanism in nanoscale magnetic multilayers.The main researches and results are as follows:(1)Effect of pass-through fluxes of Co target on the magnetic properties of thin films were studied.Co film sputtered by different pass-through fluxes(PTFs)has different remanence ratios.Cobalt film deposited by Co target with high PTF(84.21%)has lower remanence ratio(0.65),while cobalt thin film prepared by Co target with low PTF(69.13%)has higher remanence ratio(0.87).Through introducing an external magnetic field parallel to the film surface,both of the remanence ratios of cobalt films prepared by these targets can be enhanced to approach 1.HRTEM shows that cobalt thin film deposited by the target with high PTF is randomly oriented in crystallographic orientations.While,crystallographic orientations of cobalt thin film deposited by target with low PTF are relatively consistent,resulting in relatively higher remanence ratio.The external magnetic field during sputtering can drive the Co grains to arrange in a regular order with(002)orientation,leading to the improvement in remanence ratios.(2)The coercivity of Co films was tuned using the bulk defect engineering based on a Ta/Bi double buffer layer.By inserting a Bi layer into Ta/Co interface,the coercivity is increased by about 6 times compared to the Co film with only Ta buffer layer.Moreover,a further increment is observed for the Ta/Bi/Co/Ru film after 450? annealing.The XPS and PAS measurements confirm that the diffusion of Bi atoms during annealing promotes the formation of vacancy cluster,which increases the bulk defect density in the film and enhances the pinning strength of the defects on the domain walls.In addition,the Co layer shows better orientation which makes easy magnetization axis close to the film plane.These two factors lead to the increment of coercivity with increasing the annealing temperature.(3)Enhanced soft properties in CoZrTa(B)thin film with improving amorphous structure was tuned via B atoms.By introducing B atoms,in-plane coercivity show large differences that CoZrTaB film has lower coercivity than CoZrTa film.And an improving amorphous structure was found in CoZrTaB thin film compared to CoZrTa.The HRTEM measurement result confirms that the CoZrTa thin film is partially crystallized,while the CoZrTaB thin film has better amorphous morphology and shows better long-range disorder characteristics,indicating that the B atoms hinder atomic crystallization.It leads to the decreases of coercivity since there are no defects like grain boundary,dislocation,etc.to pinned magnetic domain walls and prevent the magnetic domain wall from moving,so it is easier to magnetize and has lower coercive field.These findings are crucial to optimize the magnetic properties of thin films and promote the Co based spintronic devices with high stability.(4)The magnetic properties of sputtered amorphous CoZrTa/metal-oxide(MO)were tailored by interfacial oxygen migration.As the annealing temperature Ta increases,magnetic dead layer and the in-plane coercivity(Hc)decreased,while the saturation magnetization(Ms)gets enhanced,suggesting that CoZrTa thin films show better soft magnetic properties.The oxygen migration from the CoZrTa layer up to the Al2O3 layer can effectively alter the interface structure by modifying the reconstruction of oxygen environment at the interface.While,the interfacial diffusion mechanism in CoZrTa/Metal(Pt)thin film is an important reason for the deterioration of the magnetic properties.This research gives an effective way to regulate magnetic properties of CoZrTa film and is important to enrich the scientific instruction to the development of Co-based soft magnetic thin film inductive devices.(5)The electrical properties of NiPt thin films sputtered by two NiPt targets and the phase composition of the interface between NiPt film and Si substrate were studied.The square resistance of the film sputtered by the heat-treated NiPt target sputtering was lower and the phase composition of NiPt and Si presents a low-resistance NiSi phase.In addition,by introducing a thinner Pt layer between NiPt and the Si substrate,the square resistance of the film can be further reduced and the NiSi phase structure can be optimized.It is revealed that the introduction of Pt can effectively supress the excessive diffusion of Ni to the silicon substrate and modify interface structure of NiSi.This study provide theoretical guidance for improving and optimizing the performance of metal silicide in integrated circuits and improving the performance of devices.