Significantly Improved High K Dielectric Performance: Rare Earth Oxide As a Passivation Layer Laminated with TiO2 Film

In order to achieve a super gate dielectric performance, rare earth oxides featuring for large band gap, good thermodynamic stability and relatively high k value were selected to be laminated with TiO2 film to prepare bilayer dielectric films. As an example, the microstructure, morphology, band gap structure and electrical performance of TiO2-Y2O3 bilayer films were systematically investigated. Results show that stacking sequence of TiO2 and Y2O3 sublayers has a significant impact on the dielectric performance and Y2O3 film as a passivation layer can effectively improve electrical properties. Besides, the electrical behaviors analysis of TiO2-Y2O3, Y2O3-TiO2, Y2O3 and TiO2 samples was carried out by impedance spectra and equivalent circuit. The result shows that TiO2-Y2O3/Si sample holds the largest internal resistance of 74665 ohm among four samples. Moreover, the most outstanding properties of Pt/TiO2-Y2O3/Si capacitor are achieved by varying the thickness of sublayers and annealing temperature. 500 degrees C-annealed bilayer film with 17 nm-TiO2 and 3-nm Y2O3 displays a k value of 28.24, which is more than 1.4 times that of current commercial HfO2. Further, Schottky emission was determined to be leakage current transport mechanism for TiO2-Y2O3 bilayer films. Inspired by this result, the electrical performance of more general Pt/TiO2-REOs/Si MOS capacitors (RE = Sc, La, Ce, Gd and Pr) was measured. The combination of TiO2 film and REOs passivation layer with the satisfying performance provides promising candidates for future Si-based integrated circuit (IC). (c) 2022 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.