Dielectric breakdown in HfO2 dielectrics: Using multiscale modeling to identify the critical physical processes involved in oxide degradation

Abstract

We use a multi-scale modeling to study the time-dependent dielectric breakdown of an amorphous (a-) HfO[Formula: see text] insulator in a metal–oxide–metal capacitor. We focus on the role played by electron injection in the creation of oxygen vacancies, which eventually form the percolation path responsible for dielectric breakdown. In this scenario, the electron transport through the dielectric occurs by multi-phonon trap assisted tunnelling (MPTAT) between O vacancies. Energy parameters characterizing the creation of oxygen vacancies and the MPTAT process are calculated using density functional theory employing a hybrid density functional. The results demonstrate that the formation of neutral O vacancies facilitated by electron injection into the oxide represents a crucial step in the degradation process dominating the kinetics at common breakdown fields. We further show the importance of the so-called “energetic correlation” effect, where pre-existing O vacancies locally increase the generation rate of additional vacancies accelerating the oxide degradation process. This model gives realistic breakdown times and Weibull slopes and provides a detailed insight into the mechanism of dielectric breakdown and atomistic and electronic structures of percolation paths in a-HfO[Formula: see text]. It offers a new understanding of degradation mechanisms in oxides used in the current MOSFET technology and can be useful for developing future resistive switching and neuromorphic nanodevices.

An Atomistic Model of Field-Induced Resistive Switching in Valence Change Memory

“…Current flows in HfO 2 -based VCM result from trap-assisted tunneling through defect sites created by oxygen vacancies; these defects are assumed to originate from the change in valence of the undercoordination of Hf atoms in the vicinity of these vacancies, leaving them conductive. This mechanism is supported by experimental data revealing hopping-type conduction, a linear temperature-dependence in the low-resistance state, and theoretical studies on the location and influence of oxygen vacancies on the density of states (DOS) of HfO 2 . ,, The modeling approach we develop here assumes a distribution of charge in a way that is consistent with the filamentary nature of HfO 2 VCM cells.…”

“…This mechanism is supported by experimental data revealing hopping-type conduction, 30 a linear temperature-dependence in the lowresistance state, 14 and theoretical studies on the location and influence of oxygen vacancies on the density of states (DOS) of HfO 2 . 33,42,49 The modeling approach we develop here assumes a distribution of charge in a way that is consistent with the filamentary nature of HfO 2 VCM cells.…”

Three-Dimensional Metal-Insulator-Metal Decoupling Capacitors with Optimized ZrO2 ALD Properties for Improved Electrical and Reliability Parameters

“…The characteristic lifetime data is then extrapolated to the operating electric field by fitting the data to the “linear E” model and calculating the voltage acceleration γ. This model was selected because it describes the metal-oxide bond breakage [ 24 ] while also being a more conservative model compared to the power law model used before for similar devices [ 25 ].…”

Reliability of HfO2-Based Ferroelectric FETs: A Critical Review of Current and Future Challenges

“…One fundamental issue of FE-HfO2 based devices (with respect to perovskite-ferroelectric based ones) is the high ratio between coercive field of the ferroelectric (≈ 1 MV/cm) and breakdown field of the dielectric itself (≈ 5-6 MV/cm) [20], [67], [68]. Ultimate failure of a ferroelectric memory occurs at (hard) breakdown, hence maximum endurance can be intended as the total number of repeated writing cycles prior to failure.…”