Experimental Analysis on the Interaction Between Interface Trap Charges and Polarization on the Memory Window of Metal-Ferroelectric–Insulator-Si (MFIS) FeFET
Giuk Kim, Hyojun Choi, Sangho Lee, Hunbeom Shin, Sangmok Lee, Yunseok Nam, HyunJun Kang, Seokjoong Shin, Hoon Kim, Young-Jin Lim, Kang Kim, Il‐Kwon Oh, Sang‐Hee Ko Park, Jinho Ahn, Sanghun Jeon
Abstract
In this study, we investigated the impact of unstable and stable interface trap charges (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}\text {)}$ </tex-math></inline-formula> on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula> switching in metal-ferroelectric–insulator-Si (MFIS) ferroelectric field-effect transistors (FeFETs), which vary with the thickness of the insulator. We also examine how these variations ultimately affect the various performance metrics of MFIS FeFETs. To achieve this, we varied the thickness of the insulator (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {IL}}\text {)}$ </tex-math></inline-formula> in MFIS FeFETs to 1.5, 2.0, and 2.5 nm, thereby controlling the amount of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> injected from the channel into the ferroelectric (FE)/insulator interface. As <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {IL}}$ </tex-math></inline-formula> decreases, the amount of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> increases, which amplifies the electric field across the FE layer. As a result, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula> switching enhances, and consequently, the MW characteristics of MFIS FeFETs improve. Furthermore, to analyze this in detail, we employed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> measurements on MFIS FeFETs to simultaneously extract unstable and stable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> as well as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula> and MW. The results show that as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {IL}}$ </tex-math></inline-formula> increases to 1.5, 2.0, and 2.5 nm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> during program/erase (PGM/ERS) operations decreases to 100%, 61%, and 54%, respectively. This leads to a corresponding decrease in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula> to 100%, 59%, and 52%. Additionally, after sufficient delay following the PGM/ERS operations, we observe that the proportion stable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> compared to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula> is 91%, regardless to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {IL}}$ </tex-math></inline-formula> and the remaining 9% of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {S}}$ </tex-math></inline-formula> contributes to the MW property. Consequently, as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {IL}}$ </tex-math></inline-formula> increases to 1.5, 2.0, and 2.5 nm, the net charge decreases to 100%, 61%, and 54%, resulting in MW values of 1.85, 1.05, and 0.85 V, respectively. Finally, we analyzed the impact of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {it}}$ </tex-math></inline-formula> generation as a function of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {IL}}$ </tex-math></inline-formula> on the variability and endurance characteristics of MFIS FeFETs.