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Compact gate capacitance and gate current modeling of ultra-thin (EOT ~ 1 nm and below) SiO₂ and high-k gate dielectricsLi, Fei, 1972- 28 August 2008 (has links)
Not available / text
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Selective silicon and germanium nanoparticle deposition on amorphous surfacesCoffee, Shawn Stephen, 1978- 28 August 2008 (has links)
This dissertation describes the development of a process for the precise positioning of semiconductor nanoparticles grown by hot wire chemical vapor deposition and thermal chemical vapor deposition on amorphous dielectrics, and it presents two studies that demonstrate the process. The studies entailed growth and characterization using surface science techniques and scanning electron microscopy. The two systems, Ge nanoparticles on HfO₂ and Si nanoparticles on Si₃N₄, are of interest because their electronic properties show potential in flash memory devices. The positioning technique resulted in nanoparticles deposited within 20 nm diameter feature arrays having a 6x10¹⁰ cm⁻² feature density. Self-assembling diblock copolymer poly(styrene-b-methyl methacrylate) thin films served as the patterning soft mask. The diblock copolymer features were transferred using a CHF₃/O₂ reactive ion etch chemistry into a thin film SiO₂ hard mask to expose the desired HfO₂ or Si₃N₄ deposition surface underneath. Selective deposition upon exposed pore bottoms was performed at conditions where adatom accumulation occurred on the HfO₂ or Si₃N₄ surfaces and not upon the SiO₂ mask template. The selective deposition temperatures for the Ge/HfO₂ and Si/Si₃N₄ systems were 700 to 800 K and 900 to 1025 K, respectively. Germanium nucleation on HfO₂ is limited from hot wire chemical vapor deposition by depositing nanoparticles within 67% of the available features. Unity filling of features with Ge nanoparticles was achieved using room temperature adatom seeding before deposition. Nanoparticle shape and size are regulated through the Ge interactions with the SiO₂ feature sidewalls with the adatom removal rate from the features being a function of temperature. The SiO₂ mask limited Ge nanoparticle growth laterally to within ~5 nm of the hard mask at 800 K. Silicon deposition on patterned Si₃N₄ has multiple nanoparticles, up to four, within individual 20 nm features resulting from the highly reactive Si₃N₄ deposition surface. Silicon nucleation and continued nanoparticle growth is a linear function of deposition flux and an inverse function of sample temperature. Diblock copolymer organization can be directed into continuous crystalline domains having ordered minority phases in a process known as graphoepitaxy. In graphoepitaxy forced alignment within microscopic features occurs provided certain dimensional constraints are satisfied. Graphoepitaxy was attempted to precisely locate 20 nm diameter features for selective Ge or Si deposition and initial studies are presented. In addition to precise nanoparticle positioning studies, kinetic studies were performed using the Ge/HfO₂ material system. Germanium hot wire chemical vapor deposition on unpatterned HfO₂ surfaces was interpreted within the mathematical framework of mean-field nucleation theory. A critical cluster size of zero and critical cluster activation energy of 0.4 to 0.6 eV were estimated. Restricting HfO₂ deposition area to a 200 nm to 100 [mu]m feature-width range using SiO₂ decreases nanoparticle density compared to unpatterned surfaces. The studies reveal the activation energies for surface diffusion, nucleation, and Ge etching of SiO₂ are similar in magnitude. Comparable activation energies for Ge desorption, surface diffusion and cluster formation obscure the change with temperature an individual process rate has on nanoparticle growth characteristics as the feature size changes. / text
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A study on electrical and material characteristics of hafnium oxide with silicon interface passivation on III-V substrate for future scaled CMOS technologyOk, Injo, 1974- 29 August 2008 (has links)
The continuous improvement in the semiconductor industry has been successfully achieved by the reducing dimensions of CMOS (complementary metal oxide semiconductor) technology. For the last four decades, the scaling down of physical thickness of SiO₂ gate dielectrics has improved the speed of output drive current by shrinking of transistor area in front-end-process of integrated circuits. A higher number of transistors on chip resulting in faster speed and lower cost can be allowable by the scaling down and these fruitful achievements have been mainly made by the thinning thickness of one key component - Gate Dielectric - at Si based MOSFET (metal-oxide-semiconductor field effect transistor) devices. So far, SiO₂ (silicon dioxide) gate dielectric having the excellent material and electrical properties such as good interface (i.e., Dit ~ 2x10¹⁰ eV⁻¹cm⁻²), low gate leakage current, higher dielectric breakdown immunity (≥10MV/cm) and excellent thermal stability at typical Si processing temperature has been popularly used as the leading gate oxide material. The next generation Si based MOSFETs will require more aggressive gate oxide scaling to meet the required specifications. Since high-k dielectrics provide the same capacitance with a thicker film, the leakage current reduction, therefore, less the standby power consumption is one of the huge advantages. Also, it is easier to fabricate during the process because the control of film thickness is still not in the critical range compared to the same leakage current characteristic of SiO₂ film. HfO₂ based gate dielectric is considered as the most promising candidate among materials being studied since it shows good characteristics with conventional Si technology and good device performance has been reported. However, it has still many problems like insufficient thermals stability on silicon such as low crystallization temperature, low k interfacial regrowth, charge trapping and so on. The integration of hafnium based high-k dielectric into CMOS technology is also limited by major issues such as degraded channel mobility and charge trapping. One approach to overcome these obstacles is using alternative substrate materials such as SiGe, GaAs, InGaAs, and InP to improve channel mobility. / text
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Evaluation of nitrogen incorporation effects in HfO₂ gate dielectric for improved MOSFET performanceCho, Hag-ju, 1969- 08 July 2011 (has links)
Not available / text
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Growth of Metal-Nitride Thin Films by Pulsed Laser DepositionFarrell, Ian Laurence January 2010 (has links)
The growth of thin-film metal nitride materials from elemental metal targets by plasma-assisted pulsed laser deposition (PLD) has been explored and analysed.
A new UHV PLD growth system has been installed and assembled and its system elements were calibrated. A series of GaN thin films have been grown to calibrate the system. In-situ RHEED indicated that the films were single crystal and that growth proceeded in a three-dimensional fashion. SEM images showed heavy particulation of film surfaces that was not in evidence for later refractory metal nitride films. This may be connected to the fact that Ga targets were liquid while refractory metals were solid. Most GaN films were not continuous due to insufficient laser fluence. Continuous films did not exhibit photoluminescence.
HfN films have been grown by PLD for the first time. Films grown have been shown to have high reflectivity in the visible region and low resistivity. These factors, along with their crystal structure, make them suitable candidates to be used as back-contacts in GaN LEDs and could also serve as buffer layers to enable the integration of GaN and Si technologies. Growth factors affecting the films’ final properties have been investigated. Nitrogen pressure, within the operating range of the plasma source, has been shown to have little effect on HfN films. Substrate temperature has been demonstrated to have more influence on the films’ properties, with 500 °C being established as optimum. ZrN films have also been grown by PLD. Early results indicated that they exhibit reflectivities 50 % ± 5 % lower than those of HfN. However, further growth and characterisation would be required in order to establish this as a fundamental property of ZrN as nitride targets were mostly used in ZrN production.
Single-crystal epitaxial GdN and SmN films have been produced by PLD. This represents an improvement in the existing quality of GdN films reported in the literature, which are mostly polycrystalline. In the case of SmN, these are the first epitaxial films of this material to be grown. Film quality has been monitored in-situ by RHEED which has allowed growth to be tailored to produce ever-higher crystal quality. Post-growth analyses by collaborators was also of assistance in improving film growth. Substrate temperatures and nitrogen plasma parameters have been adjusted to find optimum values for each. In addition, laser fluence has been altered to minimise the presence of metal particulates in the films, which interfere with magnetic measurements carried out in analyses. Capping layers of Cr, YSZ or AlN have been deposited on the GdN and SmN prior to removal from vacuum to prevent their degradation upon exposure to atmospheric water vapour. The caps have been steadily improved over the course of this work, extending the lifetime of the nitride films in ambient. However, they remain volatile and this may persist since water vapour can enter the film at the edge regardless of capping quality. Optical transmission has shown an onset of absorption at 1.3 eV for GdN and 1.0 eV for SmN.
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ANSA-bridged and binuclear metallocene compounds of zirconium and hafniumDiamond, Gary M. January 1994 (has links)
This thesis describes the synthesis and characterisation of new mononuclear and binuclear zirconium and hafnium compounds containing ansa-bridged ligands. Some olefin polymerization studies, employing the new compounds as catalysts, are also presented. <strong>Chapter 1</strong> begins with an introduction to Ziegler-Natta polymerization of olefins, concentrating on recently developed metallocene-based catalyst systems. The second part of the Chapter charts the development of group 4 ansa-metallocene derivatives, especially their use as stereospecific catalysts. Finally, a review of binuciear group 4 metallocene compounds containing bridging bis(cyclopentadienyl)-type ligands is presented. <strong>Chapter 2</strong> describes the synthesis and characterisation of some novel mononuclear metallocene compounds of zirconium and hafnium containing ansa-bridged ligands. The ansa-bridged mononuclear compounds [{Me<sub>2</sub>C(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)(η<sup>2</sup>-C<sub>9</sub>H<sub>6</sub>)}M(η<sup>5</sup>C<sub>5</sub>H<sub>5</sub>)Cl] (M = Zr, Hf), [{(CH<sub>2</sub>)<sub>5</sub>C(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)(η<sup>2</sup>-C<sub>9</sub>H<sub>6</sub>)}M(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Cl] (M = Zr, Hf) and [{Me<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)(η<sup>3</sup>-C<sub>13</sub>H<sub>8</sub>)}Zr(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Cl] are described, along with the X-ray crystal structures of the zirconium compounds. The η<sup>2</sup>-indenyl and η<sup>3</sup>-fluorenyl coordination modes observed for these compounds are unprecedented. The synthesis and characterisation of the novel, mononuclear ansa-bridged compounds [{Me<sub>2</sub>C(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)<sub<2</sub>}M(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Cl] (M = Zr, Hf) is also described, along with their X-ray crystal structures. The variable temperature solid state <sup>13</sup>C CP/MAS NMR spectra of [{Me<sub>2</sub>C(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)<sub<2</sub>}M(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Cl] (M = Zr, Hf) show slow rotation of the C<sub>5</sub>H<sub>5</sub> ring on the NMR timescale. <strong>Chapter 3</strong> describes the synthesis and characterisation of some novel homo- and hetero-binuclear metallocene compounds of zirconium and hafnium in which the metals are bridged by an unsymmetrical ansa ligand. The novel, chiral homobinuclear compounds [(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)MCl<sub>2</sub>{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)CMe<sub>2</sub>(η<sup>5</sup>-C<sub>9</sub>H<sub>6</sub>)}MCl<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)] (M = Zr, Hf) are described. The ansa-bridged mononuclear compounds [{Me<sub>2</sub>C(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)(η<sup>2</sup>-C<sub>9</sub>H<sub>7</sub>)M(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Cl] (M = Zr, Hf) are used as reagents for the selective synthesis of the heterobinuclear analogues [(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)MCl<sub>2</sub>{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)CMe<sub>2</sub>(η<sup>5</sup>-C<sub>9</sub>H<sub>6</sub>)}M*Cl<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)] (M = Zr, M* = Hf ; M = Hf, M* = Zr) and the unsymmetrical homobinuclear compound [(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)ZrCl<sub>2</sub>{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)CMe<sub>2</sub>(��<sup>5</sup>-C<sub>9</sub>H<sub>6</sub>)}ZrCl<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)]. The methylated derivatives [(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)M(CH<sub>3</sub>)<sub>2</sub>{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)CMe<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>6</sub>)}M*(CH<sub>3</sub>)<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)] (M = Zr, M* = Zr, Hf; M = Hf, M* = Zr, Hf) are also described. The structurally related mononuclear compounds [(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)MCl<sub>2</sub>{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)CMe<sub>2</sub>(C<sub>9</sub>H<sub>7</sub>)}] (M = Zr, Hf) and [(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Zr(CH<sub>3</sub>)<sub>2</sub>{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)CMe<sub>2</sub>(C<sub>9</sub>H<sub>7</sub>)}] have also been prepared. <strong>Chapter 4</strong> presents some olefin polymerization studies using the new compounds described in Chapter 3 as catalysts, along with either methylaluminoxane or the recently developed co-catalysts [Ph<sub>3</sub>C]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>-</sup> and B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>. <strong>Chapter 5</strong> provides the experimental details for the reactions described in this thesis and the characterising data for all new compounds are given in <strong>Chapter 6</strong> Crystallographic data for the for the X-ray structure determinations in Chapter 2 are given in the <strong>Appendices</strong>.
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Experimentelle Untersuchungen zur Diffusion von Wasserstoff und Deuterium in Nb0.8Mo0.2 und HafniumLeu, Boris. Unknown Date (has links)
Techn. Universiẗat, Diss., 2006--Darmstadt.
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A study on electrical and material characteristics of hafnium oxide with silicon interface passivation on III-V substrate for future scaled CMOS technologyOk, Injo, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.
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Studies of ultra high temperature ceramic composite components : synthesis and characterization of HfOxCy and Si oxidation in atomic oyxgen containing environmentsGeorge, Mekha Raichie. January 1900 (has links)
Thesis (Ph. D. in Chemical Engineering)--Vanderbilt University, Aug. 2008. / Title from title screen. Includes bibliographical references.
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A study of HfO₂-based MOSCAPs and MOSFETs on III-V substrates with a thin germanium interfacial passivation layerKim, Hyoung-sub, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.
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