Study On The Mechanism Of Defect Regulating Ferroelectric Properties Of HfO₂

Since the 1990s,ferroelectric memory has attracted much attention for its non-volatile,fast reading and writing speed,low power consumption and other prominent advantages.Until now,the large-scale production of ferroelectric memory is based on the traditional ferroelectric materials.However,there are many problems with traditional ferroelectric materials:they are not compatible with si-based CMOS integration process;they cause serious environmental pollution;they are of high physical thickness,etc.It is necessary to find new ferroelectric materials that can solve the above problems if ferroelectric memory is to achieve highly integrated and large-scale development.Ferroelectric properties of hafnium oxide thin film materials were first discovered in 2011.HfO₂ is compatible with si-based CMOS integration process.At the same time,it is still ferroelectric at a very low physical thickness,so it has excellent scalable ability.These properties make the ferroelectric HfO₂ thin films an ideal material for future nonvolatile memory.The ferroelectric property of HfO₂ material is derived from a metastable phase with an asymmetric crystalline phase structure that is orthorhombic phase,and the space group is Pca2₁.The generation of this crystalline phase depends on the regulation of a series of processing technologies,including the type of doped elements,doping concentration,etc.As an important means to generate ferroelectricity in HfO₂ films,the mechanism of doping is not clear.Up to now,all doped elements are acceptor elements and tetravalent elements without donor element doping.Moreover,the fatigue properties of HfO₂ films are affected by the number of oxygen vacancies,and donor doping can inhibit the parameters of oxygen vacancies.Therefore,it is necessary to explore the defect of donor doping for the ferroelectric effect of HfO₂ thin films.The most important application of ferroelectric materials is ferroelectric memory.A very important index of ferroelectric domain is its running speed,which depends on the polarization switching speed of ferroelectric domain in ferroelectric materials.However,the mechanism and influencing factors of the polarization switching kinetics of ferroelectric domains in HfO₂ thin films are not clear.Defect doping is an element that affects the ferroelectric properties of HfO₂ ferroelectric thin films.It is inevitable to know the effect of defect doping on the domain switching kinetics process?In view of the above problems,this paper explores the regulation of ferroelectric properties of HfO₂ thin films by two defects,that discusses the influence of donor element tantalum?Ta?doping on the ferroelectric properties of HfO₂ thin films,and discusses the influence of different Y element doping concentration on ferroelectric domain polarizations switching kinetics of HfO₂ thin films.In chapter 3,the preparation method of tantalum?Ta?doped hafnium oxide thin film is introduced,and the ferroelectric properties of the film were tested and analyzed.The effects of donor doping on the ferroelectric properties of HfO₂ films were investigated.It has been proved that donor doping can promote the formation of ferroelectricity in hafnium oxide thin film materials,and that the doping concentration of donor elements can regulate the ferroelectric properties of HfO₂ thin film,which provides a possibility to understand the mechanism of doping to promote the formation of ferroelectricity in HfO₂ thin film.In chapter 4,the preparation methods of yttrium?Y?doped hafnium oxide thin films are introduced,the ferroelectric properties and domain switching processes of hafnium oxide thin films with different doping components are tested and analyzed,and the effects of different doping components on the ferroelectric properties of HfO₂ thin films and the switching regulation of ferroelectric domain polarization switching are explored.It is proved that the nucleation process determines the ferroelectric domain switching speed of Y:HfO₂ thin films,and different doped components can regulate the ferroelectric properties of HYO thin films and the ferroelectric domain polarization switching speed,which improves the possibility of improving the running speed of the ferroelectric memory.