Unveiling the Unique Region Dependence of Bias Stability in Sub-μm IGZO TFTs Using Floating Channel Effect for 3D DRAM

In this letter, a unique region dependence of positive and negative bias stress (PBS/NBS) stabilities is investigated in InGaZnO (IGZO) thin-film transistors (TFTs). Based on the floating channel effect, the electric field of the channel region is solely modified with remained source and drain (S/D) region potential by applying S/D biases and grounded gate compared to traditional PBS and NBS tests, so that the role of different regions in IGZO is decoupled. A new degradation model is built to elucidate the NBS issues. It provides more direct evidence to indicate that the migration of defects in S/D region, rather than channel region, dominates NBS responses in IGZO TFTs. The effect of proposed region dependence model on PBS stability is discussed as well. This work unveils a stability mechanism in sub-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m IGZO TFTs, providing new insights into achieving reliable devices for 3D DRAM.