Enhanced Ferroelectricity and Endurance Using Nanolaminate-Gradient-Structured HfXZr1-XO₂ Films

HfO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> -based ferroelectrics are extensively researched in various fields, such as next-generation neuromorphic devices and high-density memory devices, mainly due to their remanent polarization (P <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{r}}$</tex-math> </inline-formula> , 2P <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{r}}$</tex-math> </inline-formula> ) capabilities and compatibility with CMOS processes. However, the fatigue effect that occurs when continuous electric pulses are applied to ferroelectric devices is considered one of the significant obstacles in the development and application of these devices. In this study, we proposed a new nanolaminate-gradient structured HZO (GHZO) capacitor that appropriately adjusts only the ratio of the top to bottom materials without changing the thickness and composition ratio of Hf <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{X}}$</tex-math> </inline-formula> Zr <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{1} - \text{X}}$</tex-math> </inline-formula> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> , securing better ferroelectricity and endurance compared to the existing HZO capacitors. The 2P <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{r}}$</tex-math> </inline-formula> of the GHZO sample is found to be 22.3% larger than that of the reference nonlaminated structure HZO samples when electrical pulses are applied for more than 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{6}}$</tex-math> </inline-formula> cycles. Additionally, our GHZO films show higher permittivity of 47 (GHZO1), 50 (GHZO2), and 48 (GHZO3) compared to 41 (supercycle HZO) and 37 (1-nm nanolaminate HZO), as well as an improved orthorhombic ratio after 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula> cycle pulses. These results propose a method that can be applied to the fabrication of optimal ferroelectric films in the semiconductor industry.