Structural and electrical properties of reactive magnetron sputtered yttrium-doped HfO2 films

Hafnium oxide thin films doped with different concentrations of yttrium are prepared on Si ( 100) substrates at room temperature using a reactive magnetron sputtering system. The effects of Y content on the bonding structure, crystallographic structure, and electrical properties of Y-doped HfO2 films are investigated. The x-ray photoelectron spectrum (XPS) indicates that the core level peak positions of Hf 4f and O 1s shift toward lower energy due to the structure change after Y doping. The depth profiling of XPS shows that the surface of the film is completely oxidized while the oxygen deficiency emerges after the stripping depths have increased. The x-ray diffraction and high resolution transmission electron microscopy (HRTEM) analyses reveal the evolution from monoclinic HfO2 phase towards stabilized cubic HfO2 phase and the preferred orientation of (111) appears with increasing Y content, while pure HfO2 shows the monoclinic phase only. The leakage current and permittivity are determined as a function of the Y content. The best combination of low leakage current of 10(-7) A/cm(2) at 1 V and a highest permittivity value of 29 is achieved when the doping ratio of Y increases to 9 mol%. A correlation among Y content, phase evolution and electrical properties of Y-doped HfO2 ultra-thin film is investigated.