Low Voltage High Polarization by Optimizing Scavenged WN<sub>x</sub> Interfacial Capping Layer at the Ru/Hf<sub>x</sub>Zr<sub>1‐x</sub>O<sub>2</sub> Interface and Evidence of Fatigue Mechanism
Abhijit Aich, Asim Senapati, Zhao‐Feng Lou, Yi‐Pin Chen, Shih‐Yin Huang, S. Maikap, M. H. Lee, C. W. Liu
Abstract
Abstract 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.