Defects characterization of Hybrid Floating Gate/Inter-Gate Dielectric interface in Flash memory

Zahid, Mohammed; Degraeve, R.; Breuil, L.; Blomme, Pieter; Lisoni, J. G.; bosch, G. Van den; Houdt, J. Van; Tang, B. J.

doi:10.1109/irps.2014.6860601

Cited by 4 publications

(5 citation statements)

References 25 publications

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“…However, the positive bias-temperature instability driven by electron injection into oxide films limits the gate oxide scaling in metal−HfO 2 −Si transistors [24,[58][59][60]. Furthermore, in flash cells, electron trapping in the integrated HfO 2 insulator degrades the program/erase window, retention and endurance [61,62].…”

Section: Discussionmentioning

confidence: 99%

Intrinsic electron trapping in amorphous oxide

et al. 2018

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We demonstrate that electron trapping at intrinsic precursor sites is endemic in non-glass-forming amorphous oxide films. The energy distributions of trapped electron states in ultra-pure prototype amorphous (a)-HfO insulator obtained from exhaustive photo-depopulation experiments demonstrate electron states in the energy range of 2-3 eV below the oxide conduction band. These energy distributions are compared to the results of density functional calculations of a-HfO models of realistic density. The experimental results can be explained by the presence of intrinsic charge trapping sites formed by under-coordinated Hf cations and elongated Hf-O bonds in a-HfO. These charge trapping states can capture up to two electrons, forming polarons and bi-polarons. The corresponding trapping sites are different from the dangling-bond type defects responsible for trapping in glass-forming oxides, such as SiO, in that the traps are formed without bonds being broken. Furthermore, introduction of hydrogen causes formation of somewhat energetically deeper electron traps when a proton is immobilized next to the trapped electron bi-polaron. The proposed novel mechanism of intrinsic charge trapping in a-HfO represents a new paradigm for charge trapping in a broad class of non-glass-forming amorphous insulators.

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Section: Discussionmentioning

confidence: 99%

Intrinsic electron trapping in amorphous oxide

et al. 2018

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“…In contrast to a-SiO 2 , a dominance of electron trapping is commonly observed in broad variety of high-permittivity metal oxide insulators, which suggests a different charging physics [48][49][50]. It is striking to observe that in several insulting metal oxides, such as Al 2 O 3 [39,41,51], Y 2 O 3 [40,51], HfO 2 [37,39], HfAlO x [37], GdAlO x and LaAlO x [51], deep electron traps exhibit similar energy distributions: a ≈1 eV wide band of electron energy levels is typically found in the energy range 2-3 eV below the conduction band minimum irrespective of the metal cation type or the oxide synthesis chemistry.…”

Section: Charge Trapping In Amorphous Oxidesmentioning

confidence: 99%

“…However, the positive bias-temperature instability driven by electron injection into oxide films limits the gate oxide scaling in metal-HfO 2 -Si transistors [48,49,53,54]. Furthermore, in flash cells, electron trapping in the integrated HfO 2 insulator degrades the program/erase window, retention, and endurance [50,169].…”

Section: Effect Of Charge Trapping On Functionality Of Oxide Filmsmentioning

confidence: 99%

Intrinsic charge trapping in amorphous oxide films: status and challenges

Strand

Kaviani

Gao

et al. 2018

J. Phys.: Condens. Matter

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We review the current understanding of intrinsic electron and hole trapping in insulating amorphous oxide films on semiconductor and metal substrates. The experimental and theoretical evidences are provided for the existence of intrinsic deep electron and hole trap states stemming from the disorder of amorphous metal oxide networks. We start from presenting the results for amorphous (a) HfO, chosen due to the availability of highest purity amorphous films, which is vital for studying their intrinsic electronic properties. Exhaustive photo-depopulation spectroscopy measurements and theoretical calculations using density functional theory shed light on the atomic nature of electronic gap states responsible for deep electron trapping observed in a-HfO. We review theoretical methods used for creating models of amorphous structures and electronic structure calculations of amorphous oxides and outline some of the challenges in modeling defects in amorphous materials. We then discuss theoretical models of electron polarons and bi-polarons in a-HfO and demonstrate that these intrinsic states originate from low-coordinated ions and elongated metal-oxygen bonds in the amorphous oxide network. Similarly, holes can be captured at under-coordinated O sites. We then discuss electron and hole trapping in other amorphous oxides, such as a-SiO, a-AlO, a-TiO. We propose that the presence of low-coordinated ions in amorphous oxides with electron states of significant p and d character near the conduction band minimum can lead to electron trapping and that deep hole trapping should be common to all amorphous oxides. Finally, we demonstrate that bi-electron trapping in a-HfO and a-SiO weakens Hf(Si)-O bonds and significantly reduces barriers for forming Frenkel defects, neutral O vacancies and O ions in these materials. These results should be useful for better understanding of electronic properties and structural evolution of thin amorphous films under carrier injection conditions.

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“…However, the reliability of the dielectric associated with electron trapping appears to be the "show stopper": It has already been shown that the positive bias-temperature instability (PBTI) limits the gate oxide scaling in metal-HfO 2 -Si transistors [10][11][12][13] while in flash cells, electron trapping in the intergate HfO 2 insulator degrades the program/erase window, retention, and endurance. 14,15 Moreover, in ferroelectric applications, trapping of electrons within HfO 2 will screen the electric field at the surface of the semiconductor channel, thus directly impairing the device functionality. In particular, electron injection and trapping are expected to be an issue because of the high coercive field strength typical for ferroelectric HfO 2 .…”

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confidence: 99%

Intrinsic electron traps in atomic-layer deposited HfO2 insulators

Cerbu

Madia

Andreev

et al. 2016

Applied Physics Letters

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Analysis of photodepopulation of electron traps in HfO2 films grown by atomic layer deposition is shown to provide the trap energy distribution across the entire oxide bandgap. The presence is revealed of two kinds of deep electron traps energetically distributed at around Et ≈ 2.0 eV and Et ≈ 3.0 eV below the oxide conduction band. Comparison of the trapped electron energy distributions in HfO2 layers prepared using different precursors or subjected to thermal treatment suggests that these centers are intrinsic in origin. However, the common assumption that these would implicate O vacancies cannot explain the charging behavior of HfO2, suggesting that alternative defect models should be considered.

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Defects characterization of Hybrid Floating Gate/Inter-Gate Dielectric interface in Flash memory

Cited by 4 publications

References 25 publications

Intrinsic electron trapping in amorphous oxide

Intrinsic electron trapping in amorphous oxide

Intrinsic charge trapping in amorphous oxide films: status and challenges

Intrinsic electron traps in atomic-layer deposited HfO2 insulators

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