Spectroellipsometric assessment of HfO2 thin films

Buiu, O.; Lu, Yi; Mitrović, Ivona Z.; Hall, Steve; Chalker, Paul R.; Potter, Richard J.

doi:10.1016/j.tsf.2005.12.215

Cited by 31 publications

(23 citation statements)

References 13 publications

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“…The same trend was found in C-V measurements on the same samples. 13,16 However, the dielectric constants were found to be higher ͑between 50% and 70%͒ than reported here. The strong discrepancy between the static dielectric constants from previous electrical and present infrared measurements is not clear at this point.…”

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confidence: 77%

“…The homogeneity and Al content of the films were determined by spectroscopic ellipsometry in the ultraviolet and visible spectral regions and by Auger spectroscopy, respectively. 13 Spectroscopic ellipsometry is a well-known technique for the determination of the dielectric function ͑DF͒ and thickness d of thin films within layered samples. 12 The ellipsometric parameters ⌿ and ⌬ are related to the complex reflectance ratio = r p / r s = tan ⌿ exp͑i⌬͒, where r p and r s are the reflection coefficients for light polarized parallel ͑p͒ and perpendicular ͑s͒ to the plane of incidence, respectively.…”

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confidence: 99%

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Dielectric constants and phonon modes of amorphous hafnium aluminate deposited by metal organic chemical vapor deposition

Bundesmann

Buiu

Hall

et al. 2007

Applied Physics Letters

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Dielectric constants and long-wavelength optical phonon modes of amorphous hafnium aluminate films with a maximum aluminum content of 19at.% are studied by infrared spectroscopic ellipsometry (IRSE). The hafnium aluminate films were prepared by metal organic chemical vapor deposition on silicon substrates. IRSE revealed one polar lattice mode and one impurity-type mode, which show all a systematic shift in frequency with varying Al content. The static dielectric constant decreases from 10.1 for 4.6at.% Al to 8.1 for 19at.% Al. The absolute values were found to be between 50% and 70% smaller than the values obtained from electrical measurements.

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confidence: 77%

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confidence: 99%

Dielectric constants and phonon modes of amorphous hafnium aluminate deposited by metal organic chemical vapor deposition

Bundesmann

Buiu

Hall

et al. 2007

Applied Physics Letters

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“…The ellipsometric characterization of high-k dielectric films presents a series of challenges associated with: a) Relatively (ultra) thin films with a structure dependent on the growth/deposition technique used; b) The existence of a multi-stack structure, due to the presence of a transition layer at the interface between substrate and the metal oxide film and a possible variation in the layer composition; c) The lack of reliable information on optical constants. Previously, we successfully demonstrated the use of spectroellipsometry (SE) for the characterization of HfO 2 [1,2], Hf Aluminates [3] and Hf silicates [4].…”

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confidence: 99%

Ellipsometric analysis of mixed metal oxides thin films

Buiu

Davey

et al. 2008

Thin Solid Films

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“…Examples include the use of nanometer thick metal oxides such as MgO and Al 2 O 3 as tunnel barriers in spin tunnel junction devices, 1,2 HfO 2 and ZrO 2 as alternate gate dielectrics in advanced transistor devices, [3][4][5] and Ta 2 O 5 in corrosion-resistant coatings. 6,7 In such cases, it is extremely important to understand the rate of oxidation and how it can be controlled precisely to enable stoichiometric oxide formation.…”

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A Theoretical Approach to Investigate Low-Temperature Nanoscale Oxidation of Metals under UV Radiation

Chang

Ramanathan

2007

J. Electrochem. Soc.

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The oxidation of metals at low temperatures is important not only from a fundamental point of view but also from technological relevance. Recent research has demonstrated that the nanoscale oxidation of metals such as Zr can be significantly altered during photon radiation. While there have been some experimental results to this effect, there are still no quantitative models to explain the enhancement in oxidation and the resulting self-limiting oxide thickness in the presence of radiation. In this paper, we report a detailed theoretical and numerical study of UV light-enhanced low-temperature metal oxidation. This model takes into consideration oxygen adsorption and desorption at the oxide/gas interface, ionic currents within the growing oxides enhanced by the UV-induced high-field migration, as well as electronic tunnel current in the metal-oxide-oxygen systems. Compared to the low tunnel electronic current in natural oxidation ͑without UV light͒, the tunnel electronic current due to excitation in the UV-lightenhanced oxidation process is dramatically larger than the thermionic electron current, leading to an increased oxide thickness. In addition, the model is utilized to calculate the self-limiting oxide thickness as a function of temperature with and without UV radiation, including the effect of oxygen partial pressure. Our numerical calculations indicate trends consistent with reported experimental results.Low-temperature metal oxidation is an important area of research not only from a fundamental point of view to understand mechanisms of metal oxidation but also due to the technological importance of nanoscale oxides. Examples include the use of nanometer thick metal oxides such as MgO and Al 2 O 3 as tunnel barriers in spin tunnel junction devices, 1,2 HfO 2 and ZrO 2 as alternate gate dielectrics in advanced transistor devices, 3-5 and Ta 2 O 5 in corrosion-resistant coatings. 6,7 In such cases, it is extremely important to understand the rate of oxidation and how it can be controlled precisely to enable stoichiometric oxide formation. The thickness of natural oxides at room temperature is typically of the order of 1-3 nm. 8,9 It has recently been demonstrated that oxidation of metals under UV light can dramatically enhance the rate of oxidation and also lead to high-quality dielectrics that can be used in nanoelectronic devices. 10-12 While there is limited experimental data on the initial oxidation rates of different metals under UV radiation, 13,14 there are presently no theoretical models to explain this process quantitatively. Progress in modeling low-temperature oxidation of metals is less pronounced compared to the understanding of intermediate-and high-temperature oxidation regimes. A brief description of some of the original oxidation models discussing lowtemperature oxide growth are described below.1. Wagner theory. 15 The model presented a quantitative description of the oxidation mechanism by linear equations for charged defects through ionic solids. The conclusion is L ϰ ͱ t, where L is the ...

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Spectroellipsometric assessment of HfO2 thin films

Cited by 31 publications

References 13 publications

Dielectric constants and phonon modes of amorphous hafnium aluminate deposited by metal organic chemical vapor deposition

Dielectric constants and phonon modes of amorphous hafnium aluminate deposited by metal organic chemical vapor deposition

Ellipsometric analysis of mixed metal oxides thin films

A Theoretical Approach to Investigate Low-Temperature Nanoscale Oxidation of Metals under UV Radiation

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