Preparation And Properties Of Hf_0.5Zr_0.5O₂ Ferroelectric Thin Films Based On Oxygen Vacancy Control

In recent years,hafniumoid-based ferroelectric memory has become one of the most concerned new memory in scientific research and industry due to its excellent characteristics such as perfect compatibility with modern semiconductor technology,environmental protection and no pollution,small physical thickness of ferroelectric thin film and low power consumption.The preparation technology of hafnium oxide based ferroelectric thin films determines its ferroelectric properties and is the basis and key of the development of ferroelectric memory.In this thesis,the effect of oxygen vacancy content in the film on the properties of zirconium-doped hafnium-based ferroelectric thin films was explored by optimizing the atomic layer deposition process parameters of hafnium-based ferroelectric thin films and post-treatment of low energy oxygen ions on the surface,and excellent hafnium-based ferroelectric thin films with excellent properties were prepared.The main contents are as follows:(1)The effects of reaction sources,reaction cavities and substrates on the ferroelectric properties of Hf_0.5Zr_0.5O₂(HZO)thin films in atomic layer deposition were studied.Through process optimization,ferroelectric thin films with good properties were prepared on heavily doped silicon substrate.The remanent polarization of HZO at 15 nm thickness reached 20.9?C/cm²,and the leakage current density was about 8×10^-5 A/cm²@8 V.(2)The effect of oxygen vacancy on the electrical properties of HZO ferroelectric thin films during the growth of atomic-layer deposited films was studied.The X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and electrical properties of crystalline Ti N/HZO(15 nm)/Ti N(MFM)structure samples showed that the oxygen vacancy increased.The orthogonal ferroelectric phase ratio can be increased to improve the polarization performance of the films,but the endurance performance becomes worse with the increase of leakage current density.(3)The influence of surface low-energy oxygen plasma post-treatment on the electrical properties of HZO ferroelectric films was studied.The XPS,XRD and electrical properties of HZO film samples showed that with the increase of oxygen plasma treatment time,the oxygen gap decreased,the monoclinic electrical phase ratio increased,the polarization decreased,and the leakage current density decreased.Compared with the films crystallized initially,the monoclinic phase proportion of the films after low temperature heat treatment increases,the polarization property decreases,the current density increases,but the endurance performance is obviously better.The film treated with oxygen plasma for 360 s has the best endurance performance,and the remanent polarization only decreases by 17.45%after 10⁸cycles.The results show that the injected oxygen ions have a great effect on the low temperature heat treatment of the films after crystallization,and the polarization property decreases slightly while the endurance performance is greatly improved.