Self-Aligned Top-Gate IGZO TFT With Stepped Structure for Suppressing Short Channel Effect
Jin Kyu Lee, Soobin An, Soo‐Yeon Lee
Abstract
In this work, the self-aligned coplanar top gate In-Ga-Zn-O thin-film transistor with a stepped substrate structure was investigated to suppress the short-channel effect. Usually, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\text {th}}$ </tex-math></inline-formula> roll-off occurs as channel length decreases due to a large gate and source/drain overlap ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \text{L}$ </tex-math></inline-formula> ), attributed to the significant diffusion of high carrier density from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{n}^{+}$ </tex-math></inline-formula> S/D regions into the main IGZO channel. In the proposed structure, the stepped structure induces gate insulator extension that covers the side edge of the main IGZO channel and protects from Ar plasma treatment, which forms <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{n}^{+}$ </tex-math></inline-formula> regions. The fabrication results show that the short-channel effect can be successfully suppressed up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> channel length with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.23~\mu \text{m}~\Delta \text{L}$ </tex-math></inline-formula> .