La Doped HZO-Based 3D-Trench Metal-Ferroelectric-Metal Capacitors With High-Endurance (>10¹²) for FeRAM Applications

Abstract

Integration density is one of the major criteria that ferroelectric (FE) capacitors must meet before they can be deployed in FeRAM memory arrays that can replace the conventional DRAM memories. In this work we demonstrate, for the first time, back-end-of-line compatible 3D-trench FE La doped hafnium zirconium oxide (HZO) based capacitors fabricated with a foot-print area of 200nm x 200nm for FeRAM applications. The capacitors are based on a trilayer stack (TiO2/La doped HZO/Nb2O5) with TiN as top and bottom electrodes. The initial wake-up of the films is dominated by domain de-pinning effect followed by other mechanisms. Pre-cycling scheme is demonstrated to wake-up the capacitor using higher bias (2.85V, 833KHz, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}$ </tex-math></inline-formula> cycles). Post wake-up, the device survives <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{12}}$ </tex-math></inline-formula> cycles with 2P <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {R}}26~\mu \text{C}$ </tex-math></inline-formula> /cm2 till the end of endurance cycling. Retention measurements performed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$85^{\text {o}}\text{C}$ </tex-math></inline-formula> show retention of >70% of the initial polarization at the end of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}\text{s}$ </tex-math></inline-formula> and ~30% polarization is projected to remain at the end of 10 years. The retention was found to be limited by the imprint effect. Our demonstration brings HZO based FE capacitors one step closer to nonvolatile FeRAM applications.