High-Voltage Amorphous InGaZnO Thin-Film Transistors With ITO-Modulated Offset Region
Guangan Yang, Weijia Song, Zuoxu Yu, Tingrui Huang, Jie Cao, Yong Xu, Huabin Sun, Weifeng Sun, Wangran Wu
Abstract
This study presents the high-voltage (HV) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with an offset region modulated by the indium–tin oxide (ITO) capping layer (ICL) near the drain side. The breakdown voltage (BV) is elevated because the offset region lowers the electric field between the gate and the drain. For the device without an ICL, a BV of 465 V and a large ON-resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} _{\text {on}}$ </tex-math></inline-formula> ) of 1000 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> are obtained at the offset region length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\text {offset}}$ </tex-math></inline-formula> ) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5 ~\mu \text{m}$ </tex-math></inline-formula> . The ICL effectively improves the ON-state characteristics of the HV device by reducing the resistance of the offset region. The output current of the TFTs increases with increasing ICL thickness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T} _{\text {ICL}}$ </tex-math></inline-formula> ) due to the elevated electron density in the ITO film. The a-IGZO TFT achieves a BV of 326 V and a low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} _{\text {on}}$ </tex-math></inline-formula> of 207 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> with an offset region length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\text {offset}}$ </tex-math></inline-formula> ) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5 ~\mu \text{m}$ </tex-math></inline-formula> and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T} _{\text {ICL}}$ </tex-math></inline-formula> of 11.4 nm. The gate dielectric near the gate corner is found to be a breakdown weak point due to the electric field crowding, as confirmed by the TCAD simulations.