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 Department: Department of Materials Science
 Degree Level: Master's
 Collection: UNT Theses and Dissertations
Materials properties of ruthenium and ruthenium oxides thin films for advanced electronic applications.

Materials properties of ruthenium and ruthenium oxides thin films for advanced electronic applications.

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Date: May 2006
Creator: Lim, ChangDuk
Description: Ruthenium and ruthenium dioxide thin films have shown great promise in various applications, such as thick film resistors, buffer layers for yttrium barium copper oxide (YBCO) superconducting thin films, and as electrodes in ferroelectric memories. Other potential applications in Si based complementary metal oxide semiconductor (CMOS) devices are currently being studied. The search for alternative metal-based gate electrodes as a replacement of poly-Si gates has intensified during the last few years. Metal gates are required to maintain scaling and performance of future CMOS devices. Ru based materials have many desirable properties and are good gate electrode candidates for future metal-oxide-semiconductor (MOS) device applications. Moreover, Ru and RuO2 are promising candidates as diffusion barriers for copper interconnects. In this thesis, the thermal stability and interfacial diffusion and reaction of both Ru and RuO2 thin films on HfO2 gate dielectrics were investigated using Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). An overview of Ru and RuO2/HfO2 interface integrity issues will be presented. In addition, the effects of C ion modification of RuO2 thin films on the physico-chemical and electrical properties are evaluated.
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Study of Gate Electrode Materials on High K Dielectrics

Study of Gate Electrode Materials on High K Dielectrics

Date: August 2003
Creator: Yao, Chun
Description: This problem in lieu of thesis report presents a study on gate electrode materials on high K dielectrics, including poly-SiGe and Ru. The stability of poly-SiGe in direct contact with Hf silicon-oxynitride (HfSiON) is studied by rapid thermal annealing (RTA), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). By performing a series of RTA treatments we found that as RTA thermal budgets reach 1050 C for 30s, the poly-SiGe layer begins to intermix with the HfSiON film, as observed by TEM. The maximum annealing condition for the Hf0.14Si0.23O0.46N0.17 film to remain stable in contact with poly-SiGe is 1050 C for 20s in high purity N2(99.9%) ambient. We also found that after 1000 C annealing for 60s in a nitrogen ambient, the poly-SiGe crystal phase structure was changed from a columnar structure to a large grain structure. For a metal gate, Ru was studied to determine N2annealing effects on sheet resistance of Ru sample electrodes and electrical characterization of Ru/HfSiOx/Si stack. Results show that a pure Ru metal gate is not a good choice for high k materials since it is hard to etch off, and different annealing conditions can cause large changes in ...
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Stability of Field Emitter Arrays to Oxygen Exposures

Stability of Field Emitter Arrays to Oxygen Exposures

Date: December 2002
Creator: Godbole, Soumitra Kumar
Description: The purpose of these experiments was to determine the degradation mechanisms of molybdenum based field emitter arrays to oxygen exposures and to improve the overall reliability. In addition, we also evaluated the emission current stability of gold-coated field emitter arrays to oxygen exposures. oxygen at 1x10-6 torr was introduced into the chamber through a leak valve for different lengths of time and duty cycles. To ensure identical oxygen exposure and experimental measurement conditions, tips on half the area of the FEA were fully coated with gold and the other half were left uncoated. The emission current from the gold coated half was found to degrade much less than that from the uncoated half, in the presence of oxygen. Also in the absence of oxygen, the emission current recovery for the gold-coated side was much quicker than that for the uncoated side.
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Temperature dependent rheology of surfactant-hydroxypropyl cellulose solutions.

Temperature dependent rheology of surfactant-hydroxypropyl cellulose solutions.

Date: December 2002
Creator: Snively, C. Todd
Description: The rheology of 1-8% hydroxypropyl cellulose (HPC) solutions has been studied in the temperature range of 20-45 degrees Celsius. The results showed that the relative viscosity at each HPC concentration decreases with increasing temperature. The relative viscosity decreases drastically at about 43 degrees Celsius due to a phase transition. The influence of anionic surfactant, sodium dodecylsulfate (SDS), induced gelation of a 2% HPC solution. The HPC solutions gelled at surfactant SDS concentrations ranging from 0.4 to 1.0 critical micelle concentration (CMC). The gelation of the HPC/SDS hydrogel is explained in the surfactant SDD - bridged HPC linear polymer chains. The complex viscosity - concentration profile was determined below the CMC of the SDS - water pair. The peak itself was a function of frequency indicating the presence of two relaxation times within the gelled network.
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Application of thermomechanical characterization techniques to bismuth telluride based thermoelectric materials

Application of thermomechanical characterization techniques to bismuth telluride based thermoelectric materials

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Date: August 2002
Creator: White, John B.
Description: The thermoelectric properties of bismuth telluride based thermoelectric (TE) materials are well-characterized, but comparatively little has been published on the thermomechanical properties. In this paper, dynamic mechanical analysis (DMA) and differential scanning calorimetry data for bismuth telluride based TE materials is presented. The TE materials' tan delta values, indicative of viscoelastic energy dissipation modes, approached that of glassy or crystalline polymers, were greater than ten times the tan delta of structural metals, and reflected the anisotropic nature of TE materials. DMA thermal scans showed changes in mechanical properties versus temperature with clear hysteresis effects. These results showed that the application of DMA techniques are useful for evaluation of thermophysical and thermomechanical properties of these TE materials.
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Fabrication of MOS capacitor and transitor structure using contact photolithography.

Fabrication of MOS capacitor and transitor structure using contact photolithography.

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Date: August 2002
Creator: Su, Danni
Description: This problem in lieu of thesis report describes a practical photolithographic method to produce micro patterns on metal-oxide-semiconductor or metal-oxide-semiconductor-metal layers for electrical measurements. The desired patterns are then transferred from the photo mask to the photoresist-coated metal film by exposure, followed by wet etching. In the procedure described in this report, it was observed that microstructures as small as 27 mm with an edge roughness of ~ 2 mm can be reproducibly generated with this process. MOS capacitors and transistors structures can be fabricated by using this technique. The method described in this report requires access to only simple facilities so that it is relatively inexpensive, and the overall time required for the whole process is short.
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Influence of design and coatings on the mechanical reliability of semiconductor wafers.

Influence of design and coatings on the mechanical reliability of semiconductor wafers.

Date: August 2002
Creator: Yoder, Karl J.
Description: We investigate some of the mechanical design factors of wafers and the effect on strength. Thin, solid, pre-stressed films are proposed as a means to improve the bulk mechanical properties of a wafer. Three-point bending was used to evaluate the laser scribe density and chemical processing effect on wafer strength. Drop and strike tests were employed to investigate the edge bevel profile effect on the mechanical properties of the wafer. To characterize the effect of thin films on strength, one-micron ceramic films were deposited on wafers using PECVD. Coated samples were prepared by cleaving and were tested using four-point bending. Film adhesion was characterized by notched four-point bending. RBS and FTIR were used to obtain film chemistry, and nanoindentation was used to investigate thin film mechanical properties. A stress measurement gauge characterized residual film stress. Mechanical properties of the wafers correlated to the residual stress in the film.
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Mechanical Properties of Polymer Modified Mortar

Mechanical Properties of Polymer Modified Mortar

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Date: August 2002
Creator: Palos, Artemio
Description: The mechanical properties of the polymer-modified mortar are markedly improved over conventional cement mortar. We utilized recycled ABS in powder form and a polymer latex emulsion, polymer percentage ranges from 0 to 25 percent by polymer/cement ratio were investigated. The mechanical properties investigated were compression strength and adhesion strength. Compression strength effects did not have an impact on adhesion strength. Adhesion strength was calculated with pullout testing apparatus designed by the author. Results indicate that recycled ABS had a lower adhesive strength than the acrylic latex emulsion and the base mortar, but did increase in adhesive strength when mixed with maleic-anhydride. The adhesive strength was investigated for a Fiber Reinforced Polymer (FRP) made of an "E" glass fiber that is a continuous strand roving oriented and pre-tensioned longitudinally in an isopthalic polyester matrix material. The FRP rebar was compared to standard steel rebars, and found that the standard steel corrugated rebar had a higher adhesive strength, due to mechanical interlocking. This was clarified by measurements using a smooth steel rebar. Characterization of the polymer-modified mortar was conducted by pore analysis and scanning electron microscopy. Scanning Electron Microscopy was implemented to view the polymer particles, the cement fibrils formed by the ...
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Hypotheses for Scratch Behavior of Polymer Systems that Recover

Hypotheses for Scratch Behavior of Polymer Systems that Recover

Date: May 2002
Creator: Bujard, Bernard
Description: Scratch recovery is a desirable property of many polymer systems. The reason why some materials have demonstrated excellent scratch recovery while others do not has been a mystery. Explaining the scratch resistance based upon the hardness of a material or its crosslink density is incorrect. In this thesis, novel polymers were tested in an attempt to discover materials that show excellent scratch recovery - one of the most important parameters in determining the wear of a material. Several hypotheses were developed in an attempt to give an accurate picture of how the chemical structure of a polymer affects its scratch recovery. The results show that high scratch recovery is a complex phenomenon not solely dependent upon the presence of electronegative atoms such as fluorine.
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Characterizaton of Triethoxyfluorosilane and Tetraethoxysilane Based Aerogels

Characterizaton of Triethoxyfluorosilane and Tetraethoxysilane Based Aerogels

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Date: December 2001
Creator: Roepsch, Jodi Ann
Description: Aerogels are highly porous, low dielectric constant (low k) materials being considered by the semiconductor industry as an interlayer dielectric. Low k materials are needed to overcome capacitance problems that limit device feature sizes. Precursors triethoxyfluorosilane (TEFS) and tetraethoxysilane (TEOS) were used to prepare bulk aerogels. Samples were prepared by sol-gel methods, and then carbon dioxide supercritically-dried. Effects of varying the water to precursor ratio were studied with respect to aerogel properties and microstructure. Methods of analysis for this study include FTIR-ATR, TEM, RBS, EDS, SEM, dielectric constant determination by impedance and surface area by gas adsorption. Si-F bonds were determined to be present in both acid- and base-catalyzed TEFS as well as HF-catalyzed TEOS. Fluorine promotes a fractal network microstructure as opposed to a particle-like microstructure. Surface area and dielectric constant were determined to increase slightly with increases in the water to precursor ratio.
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