Ti gate compatible with atomic-layer-deposited HfO2 for n-type metal-oxide-semiconductor devices

Yang, Hong; Son, Yunik; Baek, Sungkwon; Hwang, Hyunsang; Lim, Hajin; Jung, Hyung-Seok

doi:10.1063/1.1871362

Cited by 35 publications

(12 citation statements)

References 11 publications

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“…The metal-work function in vacuum of Ti is 4.33 eV, which is appropriate for NMOS devices. Furthermore, the Fermi-level pinning effect is not significant because the difference between the metal-work function in vacuum and the effective work function of Ti is very small [11]. Post metallization annealing was performed in a reductive gas mixture (10% H 2 and 90% N 2 ) at 400 • C for 30 min.…”

Section: Methodsmentioning

confidence: 99%

Floating Gate Memory With Biomineralized Nanodots Embedded in $\hbox{HfO}_{2}$

Ohara

Tojo

Yamashita

et al. 2011

IEEE Trans. Nanotechnology

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Memory properties of a nanodot-type floating gate memory with Co-bio-nanodots (Co-BNDs) embedded in HfO 2 were investigated. High density and uniform Co-BNDs were adsorbed on a HfO 2 tunnel oxide using ferritin. The fabricated MOS capacitor exhibited a capacitance-voltage curve with large hysteresis. The memory window size was 30 times larger than that of the MOS capacitor with an SiO 2 gate oxide. Not only a large memory window but also excellent charge retention and reliability characteristics were obtained for an MOS field-effect transistor. The high-performance nanodot-type floating gate memory was first fabricated at low temperature by utilizing supramolecular protein.

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Section: Methodsmentioning

confidence: 99%

Floating Gate Memory With Biomineralized Nanodots Embedded in $\hbox{HfO}_{2}$

Ohara

Tojo

Yamashita

et al. 2011

IEEE Trans. Nanotechnology

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“…It has been reported that the EWF may strongly depend on the processing conditions that the device is subjected to [22][23][24][25][26]. For instance, oxygen-rich or oxygen-deficient conditions can result in different interfaces [27].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, our results show that the EWF strongly depends on the type of interfaces, interface roughness and atom substitution content in interfaces, and the EWF of O-Ni interface without defects is as higher as 2.0 eV than that of Hf-Ni interface without defects. For Hf-Ni interfaces, it is found that two calculated effective work functions of interfaces without and with Ni substitution for whole interfacial Hf layer are good for nMOS and pMOS effective work function (EWF) engineering.Farther, one notices that Hf and O vacancies give rise to a considerably large EWF changes25 while Ni vacancy leads to an insensitive change of EWF. In addition, we obtain an expected theoretical relationship that variations of the EWFs are in proportion to that of interface dipole density.…”

mentioning

confidence: 99%

“…However, even so, the EWF is difficult to control, especially for pMOS, due to its extreme sensitivity to a number of factors that can alter metal-oxide interfacial electronic properties. Typically, during the actual sample deposition and integration procedures, interfacial effects, such as lattice mismatch, interface reconstruction, defect accumulation, interfacial bond formation and dipoles formation, make achieving a suitable metal gate a challenge [3,17,18], because the EWF of the metal gate could differ from its vacuum work function [19][20][21].It has been reported that the EWF may strongly depend on the processing conditions that the device is subjected to [22][23][24][25][26]. For instance, oxygen-rich or oxygen-deficient conditions can result in different interfaces [27].…”

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confidence: 99%

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Effects of intrinsic defects on effective work function for Ni/HfO2 interfaces

Zhong

Zhang

et al. 2016

Materials Chemistry and Physics

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The effective work functions and formation energies for Ni/HfO2 interfaces with and without defects, including interfacial intrinsic atom substitution and atom vacancy in interfacial layer were studied by first-principles methods based on density functional theory (DFT). The calculated results of the formation energies indicate that the interfaces with O-Ni combining bonds in the interfacial region are more energetically favorable and a small amount O vacancy is comparatively easy to form in O-Ni interface, especially under O-rich situation. Moreover, the results of our calculations also reveal that, (1) the effective work functions strongly depend on the type of interface, interface roughness and atom substitution content in the interface region;(2) for Hf-Ni interfaces, two calculated effective work functions without and with Ni substitutions in whole interfacial Hf layer are good for nMOS and pMOS effective work function (EWF) engineering, respectively; (3) the EWFs are sensitive to Hf vacancy rather than Ni vacancy in interfacial layer for Hf-Ni interfaces; (4) oxygen vacancies can result in a © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 decrease of effective work function for O-Ni interfaces. Additionally, we establish an expectedtheoretical relationship that variations of the EWFs are in proportion to that of interface dipole density. Finally, ionic valence state and occupied state are used to qualitatively analyze and explain the effects of interfacial defects on the EWF in metal-oxide interfaces. Our work suggests that controlling interfacial intrinsic atom substitution and interface roughness are attractive and promising ways for modulating the effective work function of Ni/HfO2 interfaces. IntroductionTo solve the problems arising from the aggressive size downscaling of metal-oxide-semiconductor field-effect transistor (MOSFET), both high dielectric constant "high-k" gate dielectric and metal gate electrode are required to replace the traditional SiO2 gate dielectric and polycrystalline Si, respectively [1,2]. Because of its high dielectric constant, excellent thermal stability and compatibility with various technical requirements, Hafnium oxide (HfO2) has emerged as one of the most preferred gate oxides in high-k metal gate technology [2-4]. While for desirable metal gate, an appropriate effective work function needs to satisfy the requirement that it lies near the valence and conduction band edges of Si substrate (about 4.1eV and 5.2eV for negative MOS [nMOS] and positive MOS [pMOS], respectively) [5]. There have been many studies [6-16] on tuning the effective work function (EWF) of metal-high-k gate stacks and several accompanying possible modulation methods for the EWF, such as binary 3 alloys [6], bilayer metal gate technology [7], and atomic dopant [8][9][10][11][12][13][14][15]. However, even so, the EWF is difficult to control, especially for pMOS, due to its extreme sensitivity to a number of factors th...

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“…8,9 For high-k based MOSFETs, / ef f of metals has been demonstrated to be strongly dependent on the processing conditions that the device is subjected to. [10][11][12][13][14] It has been reported that / ef f of many metal electrodes shifts toward the middle of the Si band gap upon high temperature annealing, regardless of its vacuum work function. 15 An emerging way to control the relative position of E F (or alternatively, / ef f ) is through the introduction of an interfacial dopant or "capping" layer either at the Si/HfO 2 interface or at the metal/HfO 2 interface.…”

Section: Introductionmentioning

confidence: 99%

Interface engineering through atomic dopants in HfO2-based gate stacks

Zhu

Ramanath

Ramprasad

2013

Journal of Applied Physics

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Controlling the effective work function (/ ef f) of metal electrodes is critical and challenging in metal-oxide-semiconductor field effect transistors. The introduction of atomic dopants (also referred to as "capping" layers) is an emerging approach to controllably modify / ef f. Here, we investigate the energetic preference of the location of La, Y, Sc, Al, Ce, Ti, and Zr as atomic dopants within a model Pt/HfO 2 /Si stack and the resulting variation of / ef f using density functional theory calculations. Our results indicate that all the considered atomic dopants prefer to be situated at the interfaces. The dopant-induced variation of / ef f is found to be strongly correlated to the dopant electronegativity and location. Dopants at the metal/HfO 2 interface decrease / ef f with increasing dopant electronegativity, while a contrary trend is seen for dopants at the Si/HfO 2 interface. These results are consistent with available experimental data for La, Al, and Ti doping. Our findings, especially the identified correlations, have important implications for the further optimization and "scaling down" of transistors. V

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Ti gate compatible with atomic-layer-deposited HfO2 for n-type metal-oxide-semiconductor devices

Cited by 35 publications

References 11 publications

Floating Gate Memory With Biomineralized Nanodots Embedded in $\hbox{HfO}_{2}$

Floating Gate Memory With Biomineralized Nanodots Embedded in $\hbox{HfO}_{2}$

Effects of intrinsic defects on effective work function for Ni/HfO2 interfaces

Interface engineering through atomic dopants in HfO2-based gate stacks

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