The Preparation Of New Type Hafnium-based Oxide Films And The Study Of Ferroelectric Properties

As the large-scale integrated circuit industry continues to develop toward miniaturization,SiO₂,as a gate dielectric of the traditional CMOS structure,has been unable to meet the current demand.Finding good compatibility between new ferroelectric materials and silicon-based CMOS integrated circuit technology makes it important for the development of integrated ferroelectrics.HfO₂-based nano-films have high dielectric constant?K²5?,are compatible with CMOS integrated process technology,and have ferroelectricity after special processing,making it a potential material for a new generation of gate dielectric.In this paper,HYO thin films were prepared by alternately depositing hafnium oxide ceramic targets and yttrium oxide ceramic targets on a TiN substrate by pulsed laser deposition.The effects of growth temperature,Y doping concentration,and doping method on the ferroelectric properties of HYO thin films were mainly studied.In the experiment,the small-angle grazing X-ray diffractometer?GIXRD?,piezoelectric force microscope?PFM?,and transmission electron microscope?TEM?were used to measure and analyze the crystal structure,surface morphology,interplanar spacing,thickness,and domain structure of the film;X-ray photoelectron spectroscopy?XPS?analysis of the content,ratio and atomic combination of each element in the film;Measurement of the polarization curve of a thin film capacitor structure using Radiant Precision LC system;The E4980A precision LCR tester measures the size of film capacitors and dielectric loss.The findings are as follows:The pulsed laser deposition method was used to study the HYO films with different growth temperatures?250°C,300°C,350°C?,and the surface of the films became rough as the growth temperature increased.From the GIXRD small-angle grazing test on the thin-film substrate,it can be seen that ferroelectric phases?orthogonal phases“o-111 phase”?appear at all three growth temperatures,but the ferroelectric phase?o-111?The diffraction peak is the strongest.As a result of the electrical test,the hysteresis loop obtained at a growth temperature of 250?is more ideal,has a small leakage current,and has a high dielectric constant?K²6.7?suitable for a gate dielectric.The effect of Y doping concentration on the ferroelectric properties of HYO thin films was studied.XPS measured Hf:Y atomic ratios in the HYO thin films were 3.06,3.50,and 4.75,respectively.The HYO film atomic ratio Hf:Y=3.50,the XPS characteristic peaks Hf 4f and Y 3d signals are stronger;the atomic ratio Hf:Y=3.50,the orthogonal phase diffraction peaks of the thin film crystal structure are also stronger without interference of heterogeneous phases;The electrical test atomic ratio Hf:Y=3.50,the P-E hysteresis loop and the C-V butterfly curve are also better than the other two cases.In order to obtain a more stable ferroelectric HYO thin film,the influence of doping method on the ferroelectric properties of the HYO thin film was studied.Undoped HfO₂ film,Y uniformly doped HYO film,and Y gradient doped HYO film were used.The crystal structure,thickness,and crystal plane spacing of Y-doped HYO thin films were characterized by GIXRD and transmission electron microscopy?TEM?.The crystal plane spacing results are consistent with the theoretical results.According to the characterization of each element in the thin film by EDS,it has been confirmed that the Y element in the HYO thin film is doped in a vertical direction.Y gradient doped HYO thin film electrical test has high residual polarization+P_r=10.5?C/cm²,thin film K value reaches 28,and dielectric loss is less than 0.03.The Y gradient doped HYO thin film was characterized by piezoelectric microscopy?PFM?domain structure to obtain180°domain inversion,and the domain structure inversion was still discernible after 60 minutes.It is shown that the Y gradient doped HYO thin film method can obtain an excellent ferroelectric HY thin film.In this experiment,a HYO thin film with excellent ferroelectric properties was prepared by a pulsed laser deposition method.The residual polarization was about 10?C/cm²,the dielectric constant is about 27,which is significantly higher than that of traditional gate dielectric material SiO₂?about 3.9?.The 180°domain structure inversion and the stable domain structure after 60 minutes indicate that the gradient-doped HYO film has stable ferroelectricity.