Physical origin of the endurance improvement for HfO2-ZrO2 superlattice ferroelectric film

Abstract

HfO2-ZrO2 superlattice (SL) ferroelectric (FE) ultrathin films exhibit significant improvement in endurance performance compared with solid-solution HfxZr1−xO2 (HZO). Despite the experimental evidence, the underlying microscopic mechanisms of the enhanced reliability of SL remain elusive. This Letter explores the mechanism by performing first-principle calculations on SL and HZO systems. The enhanced endurance in the SL can be well explained by higher oxygen vacancy (Vo) migration energy barriers along the FE polarization direction, which slow down the increase in Vo. The suppression of Vo increase will potentially help maintain the stability of the FE phase and alleviate the fatigue. Based on this mechanism, we suggest that doping materials with higher Vo migration barriers can further improve the endurance of HfO2-based FE devices. This work facilitates the future development of HfO2-based FE devices with enhanced endurance and reliability.

Improved Endurance of Ferroelectric Hf0.5Zr0.5O2 Using Laminated-Structure Interlayer

“…Oxygen vacancy is generally regarded as the dominant defect in ferroelectric capacitors. It is reported that the migration barriers from interfaces in HZO and laminated structures are different [ 38 ]. The vertical migration of oxygen vacancies can be suppressed in a laminated structure due to the higher energy barriers.…”

Tunable defect engineering of Mo/TiON electrode in angstrom-laminated HfO2/ZrO2 ferroelectric capacitors towards long endurance and high temperature retention

“…Obviously, AL-HZO exhibits superior endurance than SS-HZO by three orders of magnitude. This is due to the higher Vo migration barrier in AL-HZO than SS-HZO [16]. In addition, the B3 gate-stack outperforms the A gate-stack in endurance by two orders of magnitude, enduring up to 10 11 cycles.…”

“…Migita et al proposed the unbalanced bonding strengths in the nanolaminated film are enhanced at the HfO 2 and ZrO 2 interfaces [15]. Figures 1(a) and (b) depicts the energy changes of Vo migrations in the solid-solution (SS) and angstrom-laminated (AL)-HZO using first-principles calculations; it is seen that AL-HZO with a periodic stacking of 7.5 Å exhibits a higher energy barrier than SS-HZO, thus suppressing Vo migration [16]. Figure 1(c) displays x-ray photoelectron spectroscopy (XPS) Hf4f and Zr3d spectra, Voassociated bonds is less dominant in the AL-HZO, revealing AL-HZO exhibits lower Vo content [17].…”

Influence of Biaxial Strain and Interfacial Layer Growth on Ferroelectric Wake-Up and Phase Transition Fields in ZrO2

“…The electrical properties of thinner films, which are of interest for low-power memory devices, are strongly influenced by the interfacial layer (IL) formed during the film growth. It has been discussed that the remanent polarization, − cycling endurance, , and fatigue stability can be improved by utilizing a HfO 2 –ZrO 2 superlattice compared to HZO solid solution. A laminated layer with a thickness between 0.5 and 2 nm on the interface has been reported to be effective in preventing defects and dead layer formation. , Therefore, to identify if film growth conditions in the atomic layer deposited ZrO 2 produce film stresses of a similar nature in thicker and thinner ZrO 2 films, the effect of the interfacial layer must be specifically considered.…”