Relation Between Thickness and TFTs Properties of HfO2 Dielectric Layer Synthesized by Plasma-Enhanced Atomic Layer Deposition

The advancement of portable high-definition organic light-emitting diode (OLED) displays necessitates thin film transistors (TFTs) with low power consumption and high pixel density. Amorphous indium gallium zinc oxide (a-IGZO) TFTs are promising candidates to meet these requirements. However, conventional silicon dioxide gate insulators provide limited channel modulation due to their low dielectric constant, while alternative high-k dielectrics often suffer from high leakage currents and poor surface quality. Plasma-enhanced atomic layer deposition (PEALD) enables the atomic-level control of film thickness, resulting in high-quality films with superior conformality and uniformity. In this work, a systematic investigation was conducted on the properties of HfO₂ films and the electrical characteristics of a-IGZO TFTs with different HfO₂ thicknesses. A <i>Vth</i> of -0.9 V, <i>μ_sat</i> of 6.76 cm²/Vs, <i>SS</i> of 0.084 V/decade, and <i>I_on</i>/<i>I_off</i> of 1.35 × 10⁹ are obtained for IGZO TFTs with 40 nm HfO₂. It is believed that the IGZO TFTs based on a HfO₂ gate insulating layer and prepared by PEALD can improve electrical performance.