Systematic Decomposition of the Positive Bias Stress Instability in Self-Aligned Coplanar InGaZnO Thin-Film Transistors

Abstract

We propose an experimental method to decompose the positive gate-bias stress (PBS)-induced threshold voltage shift ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\mathsf {th}})$ </tex-math></inline-formula> of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) into the contributions of distinct degradation mechanisms. Top-gate self-aligned coplanar structure TFTs are used for this letter. Stress-time-divided measurements, which combine the subgap density-of-states (DOS) extraction and the analysis on recovery characteristics, are performed to separate the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\mathsf {th}}$ </tex-math></inline-formula> components. Change in excess oxygen ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{\mathsf {ex}})$ </tex-math></inline-formula> -related DOS is clearly observed, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\mathsf {th}}$ </tex-math></inline-formula> by PBS is quantitatively decomposed into the contributions of the active <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{\mathsf {ex}}$ </tex-math></inline-formula> , and the deep and shallow gate insulator traps. The quantitative decomposition of PBS-induced <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\mathsf {th}}$ </tex-math></inline-formula> provides physical insight and key guidelines for PBS stability optimization of a-IGZO TFTs.