Memory Properties of Zr-Doped ZrO2 MOS-like Capacitor

Abstract

The high-k-based MOS-like capacitors are a promising approach for the domain of non-volatile memory devices, which currently is limited by SiO2 technology and cannot face the rapid downsizing of the electronic device trend. In this paper, we prepare MOS-like trilayer memory structures based on high-k ZrO2 by magnetron sputtering, with a 5% and a 10% concentrations of Zr in the Zr–ZrO2 floating gate layer. For crystallization of the memory structure, rapid thermal annealing at different temperatures between 500 °C and 700 °C was performed. Additionally, Al electrodes were deposited in a top-down configuration. High-resolution transmission electron microscopy reveals that ZrO2 has a polycrystalline–columnar crystallization and a tetragonal crystalline structure, which was confirmed by X-ray diffraction measurements. It is shown that the tetragonal phase is stabilized during the crystallization by the fast diffusion of oxygen atoms. The capacitance–voltage characteristics show that the widest memory window (ΔV = 2.23 V) was obtained for samples with 10% Zr annealed at 700 °C for 4 min. The charge retention characteristics show a capacitance decrease of 36% after 10 years.

Annealing Effects on the Charging–Discharging Mechanism in Trilayer Al2O3/Ge/Al2O3Memory Structures

“…However, the continued scaling of device dimensions necessitates investigating high- k dielectric materials to replace SiO 2 and avoid leakage currents as much as possible . These constraints require a finding of new memory structures based on Ge-NPs using separate multilayers or embedding them in high- k dielectrics to ensure a reduced barrier height tunnel dielectric and improved electron injection by applying lower gate bias. − Several high- k dielectric materials have been explored including hafnium oxide (HfO 2 ), aluminum oxide (Al 2 O 3 ), zirconium oxide (ZrO 2 ), lanthanum oxide (La 2 O 3 ), and lanthanide oxides. , HfO 2 has emerged as a leading candidate to replace SiO 2 due to its relatively high dielectric constant (>20), band gap (>5 eV), and thermodynamic stability on silicon up to high temperatures . Al 2 O 3 also possesses excellent leakage characteristics, low interface trap density with silicon, and high-temperature robustness, though its lower dielectric constant (∼9) may limit scalability compared to HfO 2 .…”

Preparation of Remote Plasma Atomic Layer-Deposited HfO2 Thin Films with High Charge Trapping Densities and Their Application in Nonvolatile Memory Devices

“…Additionally, the increase in leakage current owing to the decrease in film thickness degrades the memory retention characteristics, thereby leading to problems in terms of device reliability. To address these issues, researchers have been actively applying high-k materials, such as HfO 2 , Al 2 O 3 , TiO x , ZnO, and ZrO 2 , to CTLs [5][6][7][8][9][10]. High-k-based oxides exhibit advantages, including small equivalent oxide thicknesses (EOTs), large band offsets to Si, and high N t values, over conventional silicon nitride.…”