Review on high-k dielectrics reliability issues

Ribes, G.; Mitard, J.; Denais, M.; Bruyère, S.; Monsieur, F.; Parthasarathy, C.; Vincent, Emmanuel; Ghibaudo, G.

doi:10.1109/tdmr.2005.845236

Cited by 482 publications

(259 citation statements)

References 36 publications

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“…The coexistence of the negative and positive charges cannot be discerned by general electric diagnoses, which feature the effective charge behaviour only as well as SPM with charge force detector whose resolution is too poor to distinguish the vertical charge spatial separation. The positive charge layer neglected in the previous pr ogramming studies with or without modelling analysis should be taken seriously because it may have a contradictory role that not only enhances the electron tunnelling through SiO 2 film to accelerate the charging process 26 but also increases the risk of SiO 2 breakdown and the retention charge loss 39 , affecting the programming/erasing performance and the device reliability 40,41 . The uneven distribution of the positive and negative charges may reflect that the charge traps do not distribute uniformly in the nanoscale because of the grains in the HfO 2 layer, although the local morphology of the interface seems flate.…”

Section: Resultsmentioning

confidence: 99%

In situ electron holography study of charge distribution in high-κ charge-trapping memory

Yao

Huo

et al. 2013

Nat Commun

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Charge-trapping memory with high-k insulator films is a candidate for future memory devices. Many efforts with different indirect methods have been made to confirm the trapping position of the charges, but the reported results in the literatures are contrary, from the bottom to the top of the trapping layers. Here we characterize the local charge distribution in the high-k dielectric stacks under different bias with in situ electron holography. The retrieved phase change induced by external bias strength is visualized with high spatial resolution and the negative charges aggregated on the interface between Al 2 O 3 block layer and HfO 2 trapping layer are confirmed. Moreover, the positive charges are discovered near the interface between HfO 2 and SiO 2 films, which may have an impact on the performance of the chargetrapping memory but were neglected in previous models and theory.

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Section: Resultsmentioning

confidence: 99%

In situ electron holography study of charge distribution in high-κ charge-trapping memory

Yao

Huo

et al. 2013

Nat Commun

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“…To relate these energies to experimental data we distinguish optical absorption/reflection type measurements involving Frank-Condon type (vertical) excitations, and electrical thermal de-trapping measurements, where phonon-assisted electron excitations are accompanied by strong lattice relaxation. We focus on the results of so called de-trapping electical measurements 11,12,13 which are interpreted in terms of thermal ionization of shallow electron traps and demonstrate that the interpretation is consistent with thermal ionization of negative V − and V 2− vacancies.Our periodic non-local density functional calculations were carried out using atomic basis set and a B3LYP hybrid density functional 14 implemented in the CRYS-TAL03 code 15 . This method reproduces band gaps of a range of transition metal oxides 16 and allows us to carry out geometry optimization of defect structures, calculate defect electronic properties and excitation energies within the same method.…”

mentioning

confidence: 98%

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confidence: 98%

Negative oxygen vacancies in HfO2 as charge traps in high-k stacks

Gavartin

Ramo

Shluger

et al. 2006

Applied Physics Letters

331

191

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We calculated the optical excitation and thermal ionization energies of oxygen vacancies in mHfO2 using atomic basis sets, a non-local density functional and periodic supercell. The thermal ionization energies of negatively charged V − and V 2− centres are consistent with values obtained by the electrical measurements. The results suggest that negative oxygen vacancies are the likely candidates for intrinsic electron traps in the hafnum-based gate stack devices.Hafnium based oxides are currently considered as a practical solution satisfying stringent criteria for integration of high-k materials in the devices in future technology nodes. However, high-k transistor performance is often affected by high and unstable threshold potential 1 , V t , and low carrier mobility 2 . These effects are usually attributed to a high concentration of charge traps and scattering centers in the bulk of the dielectric and/or at its interface with the silicon channel. Although the reported trap densities vary greatly with fabrication techniques, the majority of data point to existence of a specific intrinsic shallow electron centre common to all HfO 2 based stacks while some extrinsic defects, such as Zr substitution in HfO 2 , have also been considered 3 .Oxygen vacancies are dominating intrinsic defects in the bulk of many transition metal oxides including HfO 2 and ZrO 2 , and are thought to be also present in high concentrations in thin films. However, in spite of numerous experimental studies, evidence relating oxygen vacancies to measured characteristics of interface traps in high-k stacks is still mostly circumstantial. Therefore, accurate theoretical characterization of these defects is highly desirable.Previous theoretical calculations of oxygen vacancy in HfO 2 and ZrO 2 reported the ground state properties obtained within local or semilocal approximations to density functional theory (DFT) methods (see 4,5 for a review). This approach, however, significantly underestimates band gaps, which hampers determining energies of defect levels with respect to the band edges and precludes identifying shallow defect states 5,6,7 . As a result, most of the early local DFT calculations (except, perhaps, ref. 8 ) failed to predict unambiguosly negative charge states of oxygen vacancy in HfO 2 . Significant improvement was achieved by Robertson et al. 4,9,10 who used screened exchange approximation to predict vacancy energy levels including V − charge state. However, these calculations were performed using a small periodic supercell and therefore corresponded to extremely high vacancy concentrations. The quality of the functional used is also largely unknown and needs independent verification.In this work we used much bigger supercells and a nonlocal functional to calculate optical excitation and thermal ionization energies of oxygen vacancies in five charge states. To relate these energies to experimental data we distinguish optical absorption/reflection type measurements involving Frank-Condon type (vertical) excitations, and electric...

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“…In the literature, breakdown analysis is commonly used as a unique tool to investigate the scaling effects on device reliability and performance. [20][21][22][23][24] Hence, not only to verify the compatibility of the proposed nucleation model, but also from the device reliability point of view, it becomes important to investigate the thickness and area dependencies of the t BD probability distributions on Cu doped Ge 0.3 Se 0.7 solid electrolyte based memory devices. Figure 7(a) shows Weibull plots of the cumulative t BD probability distributions for Ge 0.3 Se 0.7 films with thicknesses ranging from 30 to 120 nm.…”

Section: Thickness Dependencementioning

confidence: 99%

“…[20][21][22][23][24] When measuring the breakdown fields in dynamic tests or the "time-to-breakdown" in static tests, a statistical distribution is generally found. The breakdown statistics are usually related in some way to underlying random microscopic physical processes.…”

Section: Introductionmentioning

confidence: 99%

On the stochastic nature of resistive switching in Cu doped Ge0.3Se0.7 based memory devices

Soni

Meuffels

Staikov

et al. 2011

Journal of Applied Physics

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Currently, there is great interest in using solid electrolytes to develop resistive switching based nonvolatile memories (RRAM) and logic devices. Despite recent progress, our understanding of the microscopic origin of the switching process and its stochastic behavior is still limited. In order to understand this behavior, we present a statistical "breakdown" analysis performed on Cu doped Ge 0.3 Se 0.7 based memory devices under elevated temperature and constant voltage stress conditions. Following the approach of electrochemical phase formation, the precursor of the "ON resistance switching" is considered to be nucleation -the emergence of small clusters of atoms carrying the basic properties of the new phase which forms the conducting filament. Within the framework of nucleation theory, the observed fluctuations in the time required for "ON resistance switching" are found to be consistent with the stochastic nature of critical nucleus formation.

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Review on high-k dielectrics reliability issues

Cited by 482 publications

References 36 publications

In situ electron holography study of charge distribution in high-κ charge-trapping memory

In situ electron holography study of charge distribution in high-κ charge-trapping memory

Negative oxygen vacancies in HfO2 as charge traps in high-k stacks

On the stochastic nature of resistive switching in Cu doped Ge0.3Se0.7 based memory devices

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