Wake-Up Free Ferroelectric Capacitor With Quadruple-Level Storage by Inserting ZrO₂ Interlayer and Bottom Layer in HfZrO_x

Abstract

Ferroelectric (FE) HfZrOx (HZO) integrated with ZrO2 interlayer and bottom layer was explored as the new stack (TiN/HZO/ZrO2/HZO/ZrO2/TiN) for FE capacitors processed at 400 °C. The capacitors show high remnant polarization (2Pr) of 37 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{C}$ </tex-math></inline-formula> /cm2 with wake-up free behavior up to 108 long-pulse cycles. High orthorhombic phase (o-phase) ratio is confirmed to be the root cause of wake-up free behavior and both ZrO2 layers play the pivotal role as a nucleation layer for o-phase HZO formation while providing tensile stress due to large thermal expansion coefficient mismatch with HZO. Furthermore, capacitors also exhibit quadruple-level cell (4 bits/cell) operation with small device-to-device variation after long cycling. The promising results make the stack eligible for high-performance, high-reliability and high-density embedded memory applications.