Study On The Polarization Characteristics Of Al-doped Hf_0.5Zr_0.5O₂

The integration of microelectronic integrated circuits has continued to increase with the rapid development of microelectronic technology.The transition metal oxides HfO₂and ZrO₂ were widely used in the field-effect transistor gate dielectric layer due to their high dielectric constant and excellent matching with the Si lattice,replacing traditional SiO₂ materials and reducing the feature size of the device.The discovery of HfO₂-based thin film ferroelectricity has greatly promoted the development of silicon-based ferroelectric memories.Compared with traditional perovskite-type ferroelectric materials such as PZT and BST,it has good compatibility with CMOS devices,and guarantees the non-volatileness of the device at a small thickness,which was beneficial to the miniaturization of the device and the improvement of IC integration.The current research results showed that doping Zr element could stabilize the ferroelectricity of HfO₂ thin films at room temperature.When the atomic ratio of Hf to Zr was 1:1(ie,Hf_0.5Zr_0.5O₂),the ferroelectricity of the film was the strongest.Recently,obvious ferroelectric（FE）and antiferroelectric（AFE）were found in Si or Al-doped Hf_0.5Zr_0.5O₂,indicating that Si and Al could promote the formation of tetragonal phase to a lesser extent.The research work of this thesis mainly included the following:1.Using pulsed laser deposition technology,the effects of growth process parameters and heat treatment processes on Al-doped Hf_0.5Zr_0.5O₂ films were systematically studied.The results showed that with the increase of the oxygen partial pressure,the residual polarization intensity of the Al:Hf_0.5Zr_0.5O₂ thin film showed a trend of increasing and then decreasing like a convex function;The orthogonal phase diffraction peaks that promoted the ferroelectric properties of the thin film were strongest when the substrate temperature was 400℃,and the residual polarization intensity was relatively high;As the thickness of the film increased,the orthogonal diffraction peaks became weaker and the leakage current density decreased.The crystalline quality of the rapidly annealed film in nitrogen was obviously better,the increase of the annealing temperature made the leakage current density of the film larger,and the surface roughness decreased.2.TiN/1.03mol%Al:Hf_0.5Zr_0.5O₂/TiN thin film capacitor structure was prepared under the optimal growth process conditions and heat treatment process,and its microstructure and electrical were tested.The results showed that the grain size of the film surface was small and uniform.The residual polarization intensities of the thin film samples at the test voltages of 4V and 10V were 17.2μC/cm² and 23.1μC/cm²,respectively.The film leakage current density was on the order of 10^-6.3.By changing the Al content in the Hf_0.5Zr_0.5O₂ film and adjusting the process parameters,the optimal growth conditions for the undoped,2.04 mol%Al-doped and 4.00mol%Al-doped Hf_0.5Zr_0.5O₂ films were obtained.4.Analysis of the structure and electrical properties of Hf_0.5Zr_0.5O₂ films with different Al contents showed that the films had a polycrystalline phase structure.As the Al doping concentration increased and the annealing temperature decreased,the peak value of the monoclinic phase gradually decreased,and the tetragonal phase became more stable.The hysteresis loop shrank and the residual polarization decreased.With the increases of the Al content,the leakage current of the film increased significantly.For different concentrations of Al:Hf_0.5Zr_0.5O₂ film capacitors,they had different field cycling behaviors.When the Al content increased to a certain extent,the film had an antiferroelectric double electric hysteresis loop.