Effect of High-k Oxide Materials on Amorphous Indium Gallium Zinc Oxide (α-IGZO) Channel in Top Gate Field Effect Transistors

The gate dielectric material plays a significant role in high-speed transistor operation and low power consumption in field-effect transistors (FETs). A small conduction band offset energy and a large interface trap density are common problems with high-<i>k</i> dielectrics with high permittivity. For that, in this work, the integration of high-<i>k </i>dielectrics with PECVD dielectrics has been reported to show improvements in electrical performance. Here, we integrated a high-<i>k</i> dielectric with (~10 nm) amorphous indium gallium zinc oxide (<i>α</i>-IGZO) FET with different gate dielectrics PECVD (SiO₂ and Si₃N₄). In addition, using a high-<i>k</i> dielectric can help overcome the problem of plasma contamination and diffusion, which can impact the device's threshold voltage and power consumption. For that, we use two of the most promising high-<i>k </i>dielectrics (HfO₂ and Al₂O₃). Our results showed that <i>α</i>-IGZO with optimized HfO₂/SiO₂dielectrics has a superior electrical performance with high-field effect mobility (50 cm² V^-1s^-1) and an on-current of 10^-6 A, and the value of the off-current was 10^-13 A under 0.1 V_DS without any dielectric leakage. These results support the idea that increasing the gate capacitance density will improve the electrical performance and material conductivity. Integrating HfO₂ with SiO₂ improves the interface quality between the gate dielectric/channel and reduces the charge trap density and gate leakage. In contrast, there is a degradation in the electrical performance of <i>α</i>-IGZO FETs with Al₂O₃/SiO₂, related to the oxygen diffusion where more oxygen atoms diffuse from Al₂O₃ to the <i>α</i>-IGZO layer.