Anomalous V<sub>FB</sub> Shift in High-k Gate Stacks - Is its Origin at the Top or Bottom Interface ? -

Toriumi, Akira; Nabatame, Toshihide

doi:10.1149/1.3206602

Cited by 28 publications

(28 citation statements)

References 19 publications

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“…However, the O − -ion migration is expected to occur even if other types of expressions are employed, as long as the expression correctly describes the nature of O − ions with a large ionic radius. For example, similar results are obtained using the potential function proportional to 1=r 12 , which is the short-range term of the Lennard-Jones potential.…”

supporting

confidence: 65%

“…The V TH changes depend on the materials of the high-k oxide, which is attributed to the electric dipole layer that forms at the interface between the high-k oxide and the underling interfacial SiO 2 layer. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, the physics of dipole layer formation is controversial; thus, guidelines for V TH tuning using the interfacial dipole have not yet been established.…”

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confidence: 99%

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Driving force of oxygen-ion migration across high-k/SiO₂ interface

Kunugi

Nakagawa

Watanabe

2017

Appl. Phys. Express

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We clarified the mechanism of oxygen (O−)-ion migration at a high-k/SiO2 interface, which is a possible origin of the flat-band voltage shift in metal/high-k gate stacks. The oxygen density difference accommodation model was reproduced by a molecular dynamics simulation of an Al2O3/SiO2 structure, in which O− ions migrate from the higher oxygen density side to the lower one. We determined that the driving force of the O−-ion migration is the short-range repulsion between ionic cores. The repulsive force is greater in materials with a higher oxygen density, pushing O− ions to the lower oxygen density side.

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confidence: 65%

mentioning

confidence: 99%

Driving force of oxygen-ion migration across high-k/SiO₂ interface

Kunugi

Nakagawa

Watanabe

2017

Appl. Phys. Express

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“…[5][6][7] The control of the effective work function is related to the formation of dipoles at the interface between the high-κ dielectric and the interfacial SiO 2 layer underneath. [8][9][10] A schematic illustration of the location of a dipole layer is shown in Fig. 1.…”

mentioning

confidence: 99%

Low-Frequency Noise Assessment of Work Function Engineering Cap Layers in High-k Gate Stacks

Claeys

Ritzenthaler

Schram

et al. 2019

ECS J. Solid State Sci. Technol.

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Engineering the effective work function of scaled-down devices is commonly achieved by the implementation of capping layers in the gate stack. Typical cap layers are Al 2 O 3 for pMOSFETs and La-oxide or Mg for nMOSFETs. Besides introducing a dipole layer at the SiO 2 /high-κ interface, the in-diffusion of the metal ions may lead to either passivation or generation of traps in the SiO 2 /high-κ layer. This paper uses low frequency noise studies to determine the impact of capping layers on the quality of the SiO 2 /HfO 2 gate stacks. The influence on the trap profiles of different types of cap layers, different locations of the cap layer (below or on top of the HfO 2 dielectric) and the impact of different thermal budgets, typically used for the fabrication of Dynamic Random Access Memory (DRAM) logic devices, are investigated. The differences between several metal oxides are outlined and discussed.

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“…Oxygen displacement in the network due to Si's higher oxygen affinity than Ta is a possible mechanism. In fact, SiO 2 /high-κ dielectrics interfaces are known to form defects, such as dipoles (V O -I O pairs) caused by oxygen displacement (due to deferring oxygen areal densities in these materials [72,73], or oxygen vacancies [74,75]. Note, that the oxygen vacancy formation energy in Ta 2 O 5 is low compared to other high-k dielectrics [76].…”

Section: Mechanism Of the Anomalous V Th Shiftmentioning

confidence: 99%

Ta2O5/SiO2 Multicomponent Dielectrics for Amorphous Oxide TFTs

Martins

Pinto

Rovisco

et al. 2020

Electronic Materials

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Co-sputtering of SiO2 and high-κ Ta2O5 was used to make multicomponent gate dielectric stacks for In-Ga-Zn-O thin-film transistors (IGZO TFTs) under an overall low thermal budget (T = 150 °C). Characterization of the multicomponent layers and of the TFTs working characteristics (employing them) was performed in terms of static performance, reliability, and stability to understand the role of the incorporation of the high-κ material in the gate dielectric stack. It is shown that inherent disadvantages of the high-κ material, such as poorer interface properties and poor gate insulation, can be counterbalanced by inclusion of SiO2 both mixed with Ta2O5 and as thin interfacial layers. A stack comprising a (Ta2O5)x(SiO2)100 − x film with x = 69 and a thin SiO2 film at the interface with IGZO resulted in the best performing TFTs, with field-effect mobility (µFE) ≈ 16 cm2·V−1·s−1, subthreshold slope (SS) ≈ 0.15 V/dec and on/off ratio exceeding 107. Anomalous Vth shifts were observed during positive gate bias stress (PGBS), followed by very slow recoveries (time constant exceeding 8 × 105 s), and analysis of the stress and recovery processes for the different gate dielectric stacks showed that the relevant mechanism is not dominated by the interfaces but seems to be related to the migration of charged species in the dielectric. The incorporation of additional SiO2 layers into the gate dielectric stack is shown to effectively counterbalance this anomalous shift. This multilayered gate dielectric stack approach is in line with both the large area and the flexible electronics needs, yielding reliable devices with performance suitable for successful integration on new electronic applications.

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Anomalous V_FB Shift in High-k Gate Stacks - Is its Origin at the Top or Bottom Interface ? -

Cited by 28 publications

References 19 publications

Driving force of oxygen-ion migration across high-k/SiO₂ interface

Driving force of oxygen-ion migration across high-k/SiO₂ interface

Low-Frequency Noise Assessment of Work Function Engineering Cap Layers in High-k Gate Stacks

Ta2O5/SiO2 Multicomponent Dielectrics for Amorphous Oxide TFTs

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Anomalous VFB Shift in High-k Gate Stacks - Is its Origin at the Top or Bottom Interface ? -

Cited by 28 publications

References 19 publications

Driving force of oxygen-ion migration across high-k/SiO2 interface

Driving force of oxygen-ion migration across high-k/SiO2 interface

Low-Frequency Noise Assessment of Work Function Engineering Cap Layers in High-k Gate Stacks

Ta2O5/SiO2 Multicomponent Dielectrics for Amorphous Oxide TFTs

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Product

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Anomalous V_FB Shift in High-k Gate Stacks - Is its Origin at the Top or Bottom Interface ? -

Driving force of oxygen-ion migration across high-k/SiO₂ interface

Driving force of oxygen-ion migration across high-k/SiO₂ interface