Preparation And Properties Of Yttrium Doped Hafnium Oxide Nano-film Capacitors

With the down-scaling of integrated circuits,SiO₂,the conventional gate oxide dielectric layer,has been not suitable for process requirements gradually.HfO₂ thin film,a promising high-k oxide materials to replace SiO₂ as the gate dielectric material of CMOS device in the integrated circuit,has become a hot research in this field.Furthermore,a recent study has found that HfO₂-based thin films have ferroelectric properties after special process,and this discovery make it become a promising ferroelectric material to break through the barriers for the application of Ferroelectric Random Access Memories.In this paper,the HfO₂-based film has been prepared by three target co-sputtering reactive magnetron sputtering with pure hafnium and yttrium metal target.The influence of film thickness and yttrium content on the phase transformation,surface roughness and electrical performance was main analyzed.X-ray photoelectron spectroscopy（XPS）measurements were carried out to probe the atomic ratio of yttrium and hafnium as well as the bonding features.Finally,the polarization and leakage current of the film capacitor were performed by using the ferroelectric tester.In order to complete the integration of MIM structure thin film capacitor,two major problems were solved.One is to explore the prepatation process of TiN thin film electrode with good conductive,the influence of deposition temperature on the phase,surface roughness and resistivity of the TiN film was studied as well.The other is mask design and integrated process optimization.The results show that high quality Y: HfO₂ films have been successfully deposited by three target co-sputtering reactive magnetron sputtering system.The XPS analyses shows that Y element exists in the film in the form of Y2O3,and as the sputtering power of Y target increased from 0 W to 75 W,the doping concentration of Y was increased from 0 mol.% to 10.1 mol.%.When the Y content was 7.7 mol.%,the film phase existed cubic steadily at room temperature,and the crystal structure did not change to the monoclinic phase with the increase of the film thickness.By studying the effect of substrate temperature on TiN thin film electrode,the TiN thin film electrode with excellent conductivity was obtained,and the resistivity was 46 μΩ·cm.The Y:HfO₂ thin film capacitors with high dielectric constant and low leakage current were obtained in electrical performance testing.The dielectric constant of Y:HfO₂ thin film with 10.1 mol.% Y content is about 55,and the leakage current of the thin film capacitor is about 4 × 10-6 A?cm-2 under the field strength of 1 MV/cm.