Ultra-thin Atomic Layer Deposited HfO2: Tailoring Dielectric Thickness for Low-Operating Voltage Thin-Film Transistors

Abstract

To achieve low-power consumption and high performance in TFTs, it is crucial to reduce the thickness of the dielectric gate layer while maintaining a defect-free structure and high dielectric properties. This study explores the effects of varying HfO2 layer thickness on TFT performance. X-ray photoelectron spectroscopy analysis indicates a decrease in oxygen defects as the film thickness increases. The morphological and topological properties of the films were characterized using grazing incidence small and wide-angle X-ray scattering and atomic force microscopy. Impedance spectroscopy was utilized to analyze the dielectric properties, showing that the 10 nm HfO2 film exhibited a low leakage current density of 13 nA cm−2 at 1 V and a permittivity of 5.98. The fabricated ZnO TFT with a 10 nm HfO2 gate dielectric layer operated at an ultra-low voltage of -1.59 V, achieving a high current on/off ratio exceeding 106. These findings highlight the importance of controlling dielectric layer thickness for the development of high-performance TFTs and their potential for low-power microelectronic applications.