Enhancing Ferroelectricity of HfZrO<i>ₓ</i>-Based Ferroelectric Capacitors by Quenching With Liquid Nitrogen

To induce the ferroelectric (FE) phase in the HfZrOx (HZO) film, the cooling stage during the crystallization annealing process assumes a crucial role. A more rapid cooling rate typically favors the formation of a higher proportion of the orthorhombic phase, which necessitates a significant temperature difference during the cooling process. In order to establish an adequately substantial temperature difference that aligns with back-end-of-line (BEOL) compatibility, the utilization of liquid nitrogen (LN2) was implemented for rapid quenching in this study. In contrast to the conventional cooling approach within an rapid thermal annealing (RTA) chamber (a cooling rate of 3.1 °C/s), the utilization of LN2 quenching (cooling rate of 49.6 °C/s) for HZO-based FE capacitors showcases noteworthy benefits. These include a 31.5% enhancement in remanent 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>) and a 2.5-fold improvement in switching speed, enabling a promising pathway for the advancement of FE device performance.