Significantly improved high k dielectric performance: Rare earth oxide as a passivation layer laminated with TiO2 film

Abstract

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 Ω 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 °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).