The move to implement metal oxide based gate dielectrics in a metal-oxide-semiconductor field effect transistor is considered one of the most dramatic advances in materials science since the invention of silicon based transistors. Metal oxides are superior to SiO 2 in terms of their higher dielectric constants that enable the required continuous down-scaling of the electrical thickness of the dielectric layer while providing a physically thicker layer to suppress the quantum mechanical tunneling through the dielectric layer. Over the last decade, hafnium based materials have emerged as the designated dielectrics for future generation of nano-electronics with a gate length less than 45 nm, though there exists no consensus on the exact composition of these materials, as evolving device architectures dictate different considerations when optimizing a gate dielectric material. In addition, the implementation of a non-silicon based gate dielectric means a paradigm shift from diffusion based thermal processes to atomic layer deposition processes. In this report, we review how HfO 2 emerges from all likely candidates to become the new gold standard in the microelectronics industry, its different phases, reported electrical properties, and materials processing techniques. Then we use specific examples to discuss the evolution in designing hafnium based materials, from binary to complex oxides and to non-oxide forms as gate dielectric, metal gates and diffusion barriers. To address the impact of these hafnium based materials, their interfaces with silicon as well as a variety of semiconductors are discussed. Finally, the integration issues are highlighted, including carrier scattering, interface state passivation, phonon engineering, and nano-scale patterning, which are essential to realize future generations of devices using hafnium-based high- k materials.

Development of hafnium based high-k materials—A review

The valence and conduction bands of am- and γ-Al2O3 films grown by the atomic layer deposition technique were studied simultaneously in identical experimental conditions using high-resolution near -edge X-ray absorption fine structure and soft X-ray photoelectron spectroscopy. The valence band maximum was found to be centered at 3.64 ± 0.04 eV for am-Al2O3 and 3.47 ± 0.04 eV for γ-Al2O3. The band gap of Al2O3 was determined to be 7.0 ± 0.1 and 7.6 ± 0.1 eV for measured am- and γ-Al2O3, respectively. The main role in changing the band gap belongs to a shift of the bottom of conduction band depending on Al2O3 crystalline form. The position of the bottom of the conduction band is governed by the charge transfer from Al atom to the oxygen that depends strongly on the Al atom coordination symmetries. A strong p–d hybridization allowed for Td symmetry but forbidden for Oh symmetry plays the decisive role in the formation of the bottom of the conduction band.

Interpretation of the Changing the Band Gap of Al2O3 Depending on Its Crystalline Form: Connection with Different Local Symmetries

Within its rich phase diagram titanium dioxide is a truly multifunctional material with a property palette that has been shown to span from dielectric to transparent-conducting characteristics, in addition to the well-known catalytic properties. At the same time down-scaling of microelectronic devices has led to an explosive growth in research on atomic layer deposition (ALD) of a wide variety of frontier thin-film materials, among which TiO2 is one of the most popular ones. In this topical review we summarize the advances in research of ALD of titanium dioxide starting from the chemistries of the over 50 different deposition routes developed for TiO2 and the resultant structural characteristics of the films. We then continue with the doped ALD-TiO2 thin films from the perspective of dielectric, transparent-conductor and photocatalytic applications. Moreover, in order to cover the latest trends in the research field, both the variously constructed TiO2 nanostructures enabled by ALD and the Ti-based hybrid inorganic-organic films grown by the emerging ALD/MLD (combined atomic/molecular layer deposition) technique are discussed. CONTENTS

/pdf/titanium-dioxide-thin-films-by-atomic-layer-deposition-a-2g4e18lu49.pdf

Titanium dioxide thin films by atomic layer deposition: a review

An intramolecular reaction catalyzed by Rh porphyrins was studied in the presence of interfacial electric fields. 1-Diazo-3,3-dimethyl-5-phenylhex-5-en-2-one (2) reacts with Rh porphyrins via a putative carbenoid intermediate to form cyclopropanation product 3,3-dimethyl-5-phenylbicyclo[3.1.0]hexan-2-one (3) and insertion product 3,3-dimethyl-2,3-dihydro-[1,1'-biphenyl]-4(1H)-one (4). To study this reaction in the presence of an interfacial electric field, Si electrodes coated with thin films of insulating dielectric layers were used as the opposing walls of a reaction vessel, and Rh porphyrin catalysts were localized to the dielectric-electrolyte interface. The charge density was varied at the interface by changing the voltage across the two electrodes. The product ratio was analyzed as a function of the applied voltage and the surface chemistry of the dielectric layer. In the absence of an applied voltage, the ratio of 3:4 was approximately 10:1. With a TiO2 surface, application of a voltage induced a Rh porphyrin-TiO2 interaction that resulted in an increase in the 3:4 ratio to a maximum in which 4 was nearly completely suppressed (>100:1). With an Al2O3 surface or an alkylphosphonate-coated surface, the voltage caused a decrease in the 3:4 ratio, with a maximum effect of lowering the ratio to 1:2. The voltage-induced decrease in the 3:4 ratio in the absence of TiO2 was consistent with a field-dipole effect that changed the difference in activation energies for the product-determining step to favor product 4. Effects were observed for porphyrin catalysts localized to the electrode-electrolyte interface either through covalent attachment or surface adsorption, enabling the selectivity to be controlled with unfunctionalized Rh porphyrins. The magnitude of the selectivity change was limited by the maximum interfacial charge density that could be attained before dielectric breakdown.

Interfacial Electric Field Effects on a Carbene Reaction Catalyzed by Rh Porphyrins

In this work, we present the first crystal growth of cubic Tb2O3 single crystals by a controlled atmosphere flux method which uses a heavy metal free solvent working at less than half the melting temperature of this sesquioxide. Cubic millimeter-sized crystals extracted from as-grown boules are phase (powder XRD) and chemically (GDMS) pure and exhibit a Verdet constant in the visible and near-infrared spectral ranges, which is at least three times higher than that of a commercial Tb3Ga5O12 (TGG) crystal. The 1.36 mm thick crystals display a transmission coefficient higher than 77% over the 525 nm–1.38 μm spectral range. The absorption spectrum, magnetic susceptibility and specific heat measurements on the single crystals confirm the absence of detectable Tb4+ cations and other impurities.

Flux growth at 1230 °C of cubic Tb2O3 single crystals and characterization of their optical and magnetic properties

Band offsets of the Al2O3/GaSb system and various surface passivation treatments of the GaSb substrate by HCl, NH4OH, and (NH4)2S solutions were investigated by x-ray photoelectron spectroscopy. The extracted conduction and valence band offsets values of Al2O3 relative to GaSb are 2.4±0.1 eV and 3.4±0.2 eV, respectively. The presence of Ga–O and Sb–O bonds was detected after NH4OH surface treatment. In contrast, (NH4)2S and HCl solutions inhibit the Sb oxide formation. The lowest amount of Ga–O bands was obtained for (NH4)2S passivation. These results correlate with capacitance-voltage (C-V) measurements of Pd–Au/Al2O3/GaSb stacks which yielded the best characteristics for the S-based passivation.

Band offsets determination and interfacial chemical properties of the Al2O3/GaSb system

We describe the electrical properties of atomic layer deposited TiO2/Al2O3 bilayer gate oxides which simultaneously achieve high gate capacitance density and low gate leakage current density. Crystallization of the initially amorphous TiO2 film contributes to a significant accumulation capacitance increase (∼33%) observed after a forming gas anneal at 400 °C. The bilayer dielectrics reduce gate leakage current density by approximately one order of magnitude at flatband compared to Al2O3 single layer of comparable capacitance equivalent thickness. The conduction band offset of TiO2 relative to InGaAs is 0.6 eV, contributing to the ability of the stacked dielectric to suppress gate leakage conduction.

/pdf/titania-alumina-bilayer-gate-insulators-for-ingaas-metal-3qe1aigyjc.pdf

Titania/alumina bilayer gate insulators for InGaAs metal-oxide-semiconductor devices

The authors developed a new Al2O3–SiO2 (A-O) stack for application as a high voltage complementary metal oxide semiconductor (CMOS) dielectric and/or top oxide in electrically erasable programmable read only memory floating gate and polysilicon-oxide-nitride-oxide-silicon embedded memories in advanced technology nodes. An amorphous atomic layer deposited alumina is doped with nitrogen and transformed into the crystalline phase by further rapid thermal process annealing. The 65A effective oxide thickness (EOT) stack allows operating voltages twice exceeding the values for thermal SiO2 of the same EOT, has extremely low leakage currents, has negligible charge trapping, and is immune to degradation. Moreover, after alumina removal, the remaining strongly nitrided bottom oxide layer can be used as the gate dielectric of CMOS devices.

Al2O3–SiO2 stack with enhanced reliability

The energy band gap, the band alignment with Si, and the chemical bonding of 4–5 nm thick (TbxSc1−x)2O3 dielectric films were investigated as a function of composition. Films with x=0, 0.5, and 1 were prepared by a molecular beam deposition technique on silicon substrates. The structure of the dielectric films was characterized by high resolution transmission electron microscopy. We found that upon deposition, a silicate and a silicon oxide layer were formed at the dielectric/silicon interface for all compositions. X-ray photoelectron spectroscopy was used to determine the band gap, as well as the energy band alignment with Si and the chemical structure of the films. Energy gap values of 6.0±0.2 and 7.5±0.2 eV were obtained for pure Sc2O3 and Tb2O3, respectively, while for the mixed layer (x=0.5) a value of 6.8±0.2 eV was extracted. It was found that the valence band offset does not change with Sc addition to Tb2O3, while the conduction band offset increases with x, from a value of 2.9±0.2 eV for the x=0 ...

Determination of band offsets, chemical bonding, and microstructure of the (TbxSc1−x)2O3/Si system

http://ma.ecsdl.org/content/MA2010-01/17/934.full.pdf

Determination of Band Offsets, Chemical Bonding and Microstructure of the (TbxSc1-x)2O3/Si System

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

I. Geppert

Author Tools

Chat about Author