Excellent Reliability and High-Speed Antiferroelectric HfZrO₂ Tunnel Junction by a High-Pressure Annealing Process and Built-In Bias Engineering

Abstract

Hafnia-based ferroelectric tunnel junctions (FTJs) have great potential for use in logic in nonvolatile memory because of their complementary metal−oxide−semiconductor process compatibility, low power consumption, high scalability, and nondestructive readout. However, typically, ferroelectrics have a depolarization field, resulting in poor endurance owing to the early dielectric breakdown. Herein, an outstandingly reliable and high-speed antiferroelectric HfZrO tunnel junction (AFTJ) is probed to understand whether it is a promising candidate for next-generation nonvolatile memory applications. High-reliability AFTJ can be explained by less charge injection due to the low depolarized field. The formation of two stable nonvolatile states, even with antiferroelectric materials, is possible if asymmetric work function electrodes and fixed oxide charges are employed, generating a built-in bias and shifting the polarization−voltage curve. In addition, via high-pressure annealing, a critical voltage that determines the transition from the t-phase to the o-phase is effectively reduced (22%). The AFTJ shows a higher endurance property (>10 9 cycles) and faster switching speed (<30 ns) than FTJ. Hence, it is proposed that with the help of internal bias modulation and high-pressure annealing, AFTJs can be employed in next-generation memory devices.

Polarization and Resistive Switching in Epitaxial 2 nm Hf0.5Zr0.5O2 Tunnel Junctions

“…This large ER is obtained in ultrathin tunnel devices with resistance area product values of ≈160 and 65 Ω•cm 2 , which are several orders of magnitude smaller than those previously found in polycrystalline HZO ferroelectric tunnel junctions measured at a similar voltage (≈10 4 −10 6 Ω• cm 2 ). 19,22,23,35,63,70 In epitaxial films, similar resistance area product values have been reported, although conductance and ER of the junctions have been partially assigned to ionic motion. 33,34 Interestingly, in 1 nm HZO films (75% content of Hf) 36 directly grown on Si or on TiN/HZO(2.5 nm)/Pt 32 structures, where ER has been attributed to ferroelectric switching, similar small resistance values have been reported.…”

“…19−26 However, as early pointed out by Max et al, 27 and in agreement with experimental observations in other ferroelectrics, 28−30 due to filamentary conductivity and ionic-motion-related mechanisms, 31 leading to resistive switching. 3 In ultrathin hafnium oxide-based films, the reported resistance ratio between OFF and ON states (=R OFF / R ON ) 19−21,27,32−37 range from 300% 35 to 5000%, 33,34 suggesting that different mechanisms may contribute to ER. Therefore, disentangling these seemingly similar responses of disparate origins is challenging, particularly in polycrystalline hafnia films.…”

“…In ultrathin hafnium oxide-based films, the reported resistance ratio between OFF and ON states (= R OFF / R ON ) − ,,− range from 300% to 5000%, , suggesting that different mechanisms may contribute to ER. Therefore, disentangling these seemingly similar responses of disparate origins is challenging, particularly in polycrystalline hafnia films.…”

One Nanometer HfO2‐Based Ferroelectric Tunnel Junctions on Silicon

“…The 1-nm Zr:HfO 2 FTJ presented in this work demonstrates the largest polarization-driven TER and thinnest ferroelectric barrier reported thus far across all HfO 2 -based FTJ literature, desirable for scaled FTJ applications. [50] The following HfO 2 -based FTJs references are considered: epitaxial PLD-deposited MFM-structures [20,30] and MFIM-structures, [31] sputtering-deposited MFM structures, [17,39,60,61] ALD-deposited MFM structures, [62][63][64] MFIM-structures, [18,19,49,[65][66][67][68][69][70] MFS-structures [45,71,72] and MFIS-structures. [43,69,[73][74][75][76][77] Reports of non-polarization-driven resistive switching in HfO 2 -based FTJs are not considered (Supporting Information).…”

High‐Performance and High‐Endurance HfO2‐Based Ferroelectric Field‐Effect Transistor Memory with a Spherical Recess Channel

“…[2,3] Nevertheless, the commercialization of HfO 2 -FeFETs has been hindered by a few significant challenges. Although the HfO 2 thin films in metal-ferroelectric-metal (MFM) capacitors feature high endurance, [14][15][16][17][18] thus far, FeFETs with the metalferroelectric-insulator-semiconductor (MFIS) structure have exhibited relatively low endurance. [3,19,20] As the interfacial layer between HfO 2 and Si is essential, an MFIS stack that is electrically modeled as a capacitor voltage divider is developed.…”