Study On The Preparation And Electrical Properties Of Hf_xZr_1-xO₂ Ferroelectric Thin Film By ALD

Ferroelectric thin film materials have been widely used in various fields of microelectronics industry,such as lead zirconate titanate（PZT）,barium strontium titanate（BST）and many other perovskite-type ferroelectric materials have been widely used in memory storage electronic devices.However,the application of ferroelectric materials to silicon-based memory still faces some problems,such as scaling limits and incompatible CMOS technology.Hf_xZr_1-xO₂（HZO）ferroelectric thin films have attracted extensive attention of researchers in the field of microelectronics because of their advantages such as high dielectric constant,strong ferroelectric polarization,good Si process compatibility and easy preparation of nanoscale thin films.In this paper,Hf_xZr_1-xO₂ ferroelectric thin films are actively studied for better application in semiconductor devices.The main research work in this paper includes the following three aspects:1.The preparation and study of HfO₂ and ZrO₂ thin films lay a foundation for Hf_xZr_1-xO₂ thin films.ZrO₂ and HfO₂ films were grown respectively based on atomic layer deposition technology,and the microstructure of the films was analyzed.The typical characteristic peaks of Hf4f,Zr3d and Ols were observed from the XPS patterns,and it was found that the O elements in the films existed mainly in the chemistry state of Hf（Zr）-O bonds fitted by software;the XRD patterns showed that the prepared ZrO₂ and HfO₂ films had obvious diffraction peaks and were in the crystalline state.Secondly,the electrical properties of the prepared ZrO₂ thin films were analyzed,which revealed that the leakage current of the films was below 10^-7A/cm² when the applied voltage was within-2V and 2V,suggesting good insulation.2.Effects of different electrode structures and thin-film thicknesses on the electrical properties of Hf_0.5Zr_0.5O₂.The film thickness was controlled accurately using atomic layer deposition（ALD）.Additionally,Metal-ferroelectric insulator-metal capacitors with different electrode structures(TiN/Hf_0.5Zr_0.5O₂/TiN,TiN/Hf_0.5Zr_0.5O₂/Pt,Pt/Hf_0.5Zr_0.5O₂/Pt)and different ferroelectric layer(Hf_0.5Zr_0.5O₂)thicknesses were prepared to investigate its microstructure and electrical properties.The results show that the films grown with TiN as the bottom contact metal have random crystal orientation and relatively strong orthogonal phase diffraction peaks.Compared with the TiN/Hf_0.5Zr_0.5O₂/Pt and Pt/Hf_0.5Zr_0.5O₂/Pt capacitors,the TiN/Hf_0.5Zr_0.5O₂/TiN devices have higher ferroelectric residual polarization and fatigue resistance.The surface flatness deteriorates,the ferroelectric properties and the dielectric coefficient decrease when the thickness of the ferroelectric layer film increases from 10 nm to 30 nm.Therefore,film thickness should be adjusted to obtain higher polarization intensity and dielectric constant.3.Based on the TiN/Hf_0.5Zr_0.5O₂（10nm）/TiN thin film structure,the effects of Zr content（0.4-0.7）,Al₂O₃dielectric layer and annealing conditions on the electrical properties of Hf_xZr_1-xO₂ thin film were further studied.It is found that the residual polarization value of HZO can be increased and the ferroelectric properties of the films can be improved by increasing the Zr content（x=0.4）,inserting 2nm alumina layer and increasing the annealing temperature.