Interfacial modulation and optimization of the electrical properties of ZrGdOx composite films prepared using a UVO-assisted sol–gel method

Abstract

In this paper, Gd-doped ZrO₂ gate dielectric films and metal-oxide-semiconductor (MOS) capacitors structured as Al/ZrGdO_x/Si were prepared using an ultraviolet ozone (UVO)-assisted sol–gel method. The effects of heat treatment temperature on the microstructure, chemical bonding state, optical properties, surface morphology and electrical characteristics of the ZrGdO_x composite films and MOS capacitors were systematically investigated. The crystalline phase of the ZrGdO_x films appeared only at 600 °C, indicating that Gd doping effectively inhibits the crystallization of ZrO₂ films. Meanwhile, as the heat treatment temperature increased from 300 °C to 600 °C, the content of oxygen vacancies decreased from 18.57% to 11.95%, and the content of metal–hydroxyl–oxygen bonds decreased from 14.72% to 8.64%. Heat treatment temperature proved to be effective in passivating the oxygen defects and reducing the trap density within the dielectric layer. At 500 °C, the MOS capacitor exhibited the best electrical characteristics, including the highest dielectric constant (k = 19.3), the smallest hysteresis (ΔV_fb = 0.01 V), the lowest boundary trapping oxide charge density (N_bt = 2.7 × 10¹⁰ cm⁻²), and the lowest leakage current density (J = 9.61 × 10⁻⁶ A cm⁻²). Therefore, adjusting the heat treatment temperature can significantly improve the performance of ZrGdO_x composite films and capacitors, which is favorable for the application of CMOS devices in large-scale and high-performance electronic systems.