Wake-up-free properties and high fatigue resistance of HfxZr1−xO2-based metal–ferroelectric–semiconductor using top ZrO2 nucleation layer at low thermal budget (300 °C)

Abstract

Ferroelectricity and crystallinity of TiN/ZrO2/Hf xZr1− xO2 (Hf:Zr = 0.43:0.57; HZO)/SiO2/Si metal–ferroelectric–semiconductor (MFS) capacitors with a top ZrO2 nucleation layer fabricated by low-temperature processes at 300 °C of atomic layer deposition and post-metallization annealing (PMA) were systematically investigated. The HZO (10 nm)-based MFS capacitors without (w/o) and with 2- and 10-nm-thick ZrO2 films (ZrO2-2 nm and ZrO2-10 nm, respectively) were found to form an extremely thin SiO2 interfacial layer (SiO2-IL) with a thickness of one or two monolayers. The HZO film in the TiN/ZrO2/HZO/SiO2/Si capacitors formed the ferroelectric orthorhombic phase even with a low thermal budget of 300 °C; in contrast, that of the w/o capacitor exhibited a predominantly amorphous structure. This result is attributed to the polycrystalline ZrO2 film acting as a nucleation layer for the crystallization of an amorphous HZO film during PMA treatment. Therefore, the remnant polarization (2 Pr) increased in the order of w/o (2.2 µC/cm2) < ZrO2-2 nm (6.8 µC/cm2) < ZrO2-10 nm (15 µC/cm2). The endurance properties of the ZrO2-10 nm capacitor were free from the wake-up effect and exhibited less degradation because of the insertion of a thick ZrO2 film of 10 nm at the TiN/HZO interface, which promoted the preferential formation of the ferroelectric orthorhombic phase and prevented the formation of oxygen vacancies at the ZrO2/HZO interface. These results suggest that superior ferroelectricity with wake-up-free properties and higher fatigue resistance of HZO-based MFS capacitors can be achieved by a low-temperature fabrication technique (300 °C) using a top ZrO2 nucleation layer.

Toward Low-Thermal-Budget Hafnia-Based Ferroelectrics via Atomic Layer Deposition

“…The + P sw value was lower than the − P sw value for each capacitor, possibly due to the voltage drop caused by the depletion layer in the Si substrate . The ZrO 2 -10 nm capacitor exhibited a hard breakdown after field cycling for 3 × 10 5 cycles, consistent with the previous reports on HfO 2 -based MFS capacitors, whereas the w/o and ZrO 2 -2 nm capacitors continued to function even after 10 6 cycles . The earlier breakdown of the ZrO 2 -10 nm capacitor is attributed to its lower breakdown field compared with the w/o and ZrO 2 -2 nm capacitors, resulting from the fully crystallized ZrO 2 /HZO bilayer with a polycrystalline structure.…”

“…129 The ZrO 2 -10 nm capacitor exhibited a hard breakdown after field cycling for 3 × 10 5 cycles, consistent with the previous reports on HfO 2 -based MFS capacitors, whereas the w/o and ZrO 2 -2 nm capacitors continued to function even after 10 6 cycles. 121 The earlier breakdown of the ZrO 2 -10 nm capacitor is attributed to its lower breakdown field compared with the w/o and ZrO 2 -2 nm capacitors, resulting from the fully crystallized ZrO 2 /HZO bilayer with a polycrystalline structure. As a result of the wake-up effect, the +P sw and −P sw of the w/o capacitor increased by as much as ∼10% after 10 2 − 10 3 field cycling cycles compared with the pristine state, whereas the ZrO 2 -2 nm and ZrO 2 -10 nm capacitors exhibited no wake-up effect.…”

“…118−120 A new idea was proposed by Onaya et al using a ZrO 2 nucleation layer to form the HZO film with the ferroelectric o-phase in an MFS structure. 121 This concept is based on the superior characteristics of ZrO 2 films processed via the low-temperature ALD process at 300 °C (e.g., good crystallinity and predominantly o/t/c-phases). The HZO-based MFM capacitors with a ZrO 2 nucleation layer exhibited the improvement of their ferroelectricity, while those with an amorphous Al 2 O 3 layer showed smaller 2P r compared to the conventional HZO-based MFM capacitors.…”

Enhanced Ferroelectricity in Hf‐Based Ferroelectric Device with ZrO2 Regulating Layer

“…[11] However, its low remnant polarization intensity and high annealing temperature have restricted its further development. [12] In order to improve the remanent polarization intensity of Hf-based ferroelectric materials, researchers generally insert an interface layer between the electrode and the ferroelectric layer, such as TiO 2 , [13,14] Al 2 O 3 , [15,16,17] HfO 2 , [18] ZrO 2 , [19,20] La 2 O 3 , [21] CeO x , [22] etc. Among them, there are reported works on the performance improvement of ZrO 2 layer in memory [23][24][25] and ZrO 2 has good lattice matching effect with HfO 2 , which was suitable as insert layer for improving performances of Hf-based devices.…”

Low Operating Voltage, Improved Breakdown Tolerance, and High Endurance in Hf0.5Zr0.5O2 Ferroelectric Capacitors Achieved by Thickness Scaling Down to 4 nm for Embedded Ferroelectric Memory

“…It should be noted that the crystallization temperature depends not only on the film thickness but also on the film deposition technique, interface between the ferroelectric and electrode, , annealing time, and annealing pressure . That is, the temperature-thickness mapping in Figure applies to HZO films that are deposited by ALD at 300 °C with water as an oxidant, capped with TiN, and annealed under a nitrogen atmosphere for 30 s, but the opportunity to lower the crystallization temperature limit by material and process engineering does remain.…”