Laminated Ferroelectric FET With Large Memory Window and High Reliability
Hyun Jae Lee, Seung‐Geol Nam, Yunseong Lee, Kihong Kim, Duk‐Hyun Choe, Sijung Yoo, Yoonsang Park, Sanghyun Jo, Donghoon Kim, Jinseong Heo
Abstract
In this work, we report a planar Si-based ferroelectric field-effect transistor (FEFET) characterized by a high memory window (MW) of 4.79 V, ten-year retention, and pass disturb-free characteristics. This achievement is realized through the use of a 20-nm-thick laminated Hf <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{0}.{5}}$ </tex-math></inline-formula> Zr0.5O2 (L-HZO) film with Al2O3 (AO)-insertion layers (ILs). The 2.4-Å-thick AO-ILs effectively severed the bulk-HZO film and scaled down each FE-thickness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {FE}}$ </tex-math></inline-formula> ) in the L-HZO. This resulted in suppression of non-FE monoclinic phase formation to less than 10%, and more notably, an increase in the coercive field ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{C}$ </tex-math></inline-formula> ) within the FE stack. With an increase in the number of HZO-lamination ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}_{\text {HZO}}$ </tex-math></inline-formula> ), the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{C}$ </tex-math></inline-formula> was enhanced by 76% in L-HZO ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}_{\text {HZO}}$ </tex-math></inline-formula> = 4) compared to single-HZO (S-HZO). This led to an increase in effective polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {eff}}$ </tex-math></inline-formula> ), representing the portion of remnant polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {r}}$ </tex-math></inline-formula> ) uncompensated by channel-injected charge, thereby validly influencing the threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {T}}$ </tex-math></inline-formula> ) shift of FEFET. The augmented <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {eff}}$ </tex-math></inline-formula> in L-HZO (350% increase compared to S-HZO) was directly confirmed through a more pronounced <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {T}}$ </tex-math></inline-formula> shift by the change of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {r}}$ </tex-math></inline-formula> , which was 230% steeper in L-HZO compared to S-HZO. The revealed mechanism behind the enhanced MW and reliability in laminated-FE, stemming from the increased <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {eff}}$ </tex-math></inline-formula> rooted in enlarged <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{C}$ </tex-math></inline-formula> , paves the way for designing the FE-stack for high-density memory or neuromorphic applications.