Low Voltage High Polarization by Optimizing Scavenged WNx Interfacial Capping Layer at the Ru/HfxZr1‐xO₂ Interface and Evidence of Fatigue Mechanism

In this study, the double remnant polarization (2P r ) is enhanced from ≈2 to 25 µC cm −2 at a low applied voltage of ±2 V (or from 10 to 35 µC cm −2 at a voltage of ±4 V) by decreasing the WN x interfacial capping layer (ICL) thickness from 6 to 2 nm in a novel Ru/WN x ICL/Hf 0.5 Zr 0.5 O 2 (HZO)/TiN structure after annealing at 400 °C in a furnace. This occurs because of the higher orthorhombic (o) plus rhombohedral (r) phases (>70%), which is analyzed by geometrical phase analysis (GPA) of high‐resolution transmission electron microscope (HRTEM) images. An optimized 2 nm WN x ICL memory capacitor shows a low coercive field (E c ) of 1.27 MV cm −1 and long endurance of > 10 9 cycles (remaining 2P r value of 13.5 µC cm −2 ) under a low field stress of ±2 MV cm −1 and 0.1 µs hold pulse width (or ≈1.67 MHz). Even this long endurance of > 10 9 cycles is obtained by applying a higher stress of ±2 MV cm −1 , 1 MHz, or 100 kHz. Under ±3 MV cm −1 stress, the mechanism is caused by m‐phase growth from both the HZO/TiN bottom electrode (BE) and WN x ICL/HZO interfaces, which is evidenced by HRTEM images after 2 × 10 7 cycles for the first time.