Preparation Of Hafnium Dioxide Thin Films By Magnetron Sputtering And Study On Their Properties

With the rapid development of microelectronics industry,the integration degree of electronic device increases sharply and device has become smaller and smaller.To avoid short-channel effect,traditional gate dielectric material SiO₂ becomes extraordinarily thin which enlarges leakage current,so SiO₂ is no longer compatible for the microelectronic devices.HfO₂thin films have become an ideal substitute for SiO₂ because of its high dielectric constant.The discovery of ferroelectricity of HfO₂ thin film has made it a promising dielectric material in ferroelectric random access memory and ferroelectric field effect transistor.HfO₂ thin films were deposited on p-type（100）silicon substrates by middle frequency magnetron sputtering.The effects of Y doping concentration,film thickness and deposition temperature on the properties of the thin films were investigated.X-ray photoelectron spectroscopy（XPS）was used to analyze the Y-doping concentration and the chemical state of each element.X-ray reflectivity（XRR）was used to measure the thickness and density of the thin films.Grazing incidence X-ray diffraction（GIXRD）was utilized to analyze the phase structure of the HfO₂ thin films.Atomic force microscopy（AFM）was utilized to investigate the surface morphology and roughness of the samples.The electrical properties of HfO₂ thin film based MIS capacitors were measured by Radiant electrical tester.The P-E curves and J-E curves were obtained to determine the relationship between the electrical properties and the experimental parameters.Finally,based on the principle of interfacial layer voltage separation,the influences of SiO₂ on the electrical properties were discussed in detail.The results show that high-k and ferroelectric HfO₂ thin films were successfully prepared by magnetron sputtering.For the HfO₂ films deposited at room temperature,when the Y dopant content increased from 0 mol.%to 9.14 mol.%,the phase transformation from monoclinic to cubic phase was observed,and the density of the sample increased firstly but decreased slightly when Y content was high,meanwhile,the surface roughness increased.The dielectric constants of the films increased as Y content increased,and the leakage current density gradually decreased.With the increase of film’s thickness,the density decreased gradually and the surface became rough.For HfO₂ thin film based MIS capacitors,when the thickness of the film increased,the dielectric constants increased.Based on the principle of dielectric interfacial layer voltage division,the series structure model of TiN/Y:HfO₂/SiO₂/Si capacitors was used to explain the facts in this work.When the electric field was constant,higher the leakage current density was observed in thicker film.As for 1.21 mol.%Y doped HfO₂ thin film,when the deposition temperature increased from room temperature to 400?C,phase transformation occurred,and the deposition rate decreased,the density increased dramatically,the roughness decreased at the same time.For MIS structure capacitors with 1.21 mol.%Y dopant concentration,the electrical behavior of Y:HfO₂ thin films gradually transited from paraelectric to ferroelectric behavior as the deposition temperature increased from room temperature to 400?C.When the deposition temperature was 400?C,the electrical behavior of the films was completely ferroelectric,and the residual polarization intensity（Pr）of the film was 9.13μC/cm²,lowest leakage current density was obtained at the same time.