Browsing by Author "Dr. Gregory Parsons, Committee Member"

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Electronica Devices and Interface Strategies for Nanotechnology
(2007-04-12) Di Spigna, Neil Halen; Dr. Veena Misra, Committee Member; Dr. Paul Franzon, Committee Chair; Dr. John Muth, Committee Member; Dr. Gregory Parsons, Committee Member
Evaporation of ultra-thin layers of refractory metals onto glass substrates represents a relatively simple method of fabricating discontinuous metal films. The utility of these films in nanotechnology is based on the ability to control their morphology. In this thesis, control of discontinuous palladium films is demonstrated as the morphology is tailored for various applications. First, the films are successfully engineered to provide molecular scaffolding in the NanoCell. A dependency of the film morphology on the pattern density is observed which potentially could be exploited to provide wafer-scale morphology tuning with only a single evaporation. Next, electrical characterization of gold nanocrystal capacitors showed significant increases in the flat band voltage shift as the gold particle density increased. The density scaling of gold and palladium films was investigated revealing a linear dependence of gold on decreasing evaporation thickness and an exponential dependence for palladium. A palladium particle density of 1.03 x 10¹² particles cm⁻² was achieved, exceeding the theoretical target density for non-volatile memory applications. A novel technique to further increase this particle density is demonstrated. Another application for discontinuous metal films is for stochastic interface strategies. Interfacing the nanoworld with the microworld represents a critical challenge to fully integrated nanosystems. Unfortunately, not all applications can tolerate random or incomplete connectivity that can result from stochastic solutions. Therefore, a novel structure is presented that permits complete and deterministic cross-connect of orthogonal wiring arrays without the need for any critical translational alignment. Deterministically connecting 10nm wires directly to 3 µ wires would require a translational alignment to within only about 6 µ. It is shown that there is no restriction placed on the minimum nanowire pitch and that the design is independent of the technology used to fabricate the nanowires. The process is relatively simple and is presented from a fabrication perspective, critically evaluating the effect of potential processing errors on the design. A proof-of-concept structure is fabricated and analyzed, demonstrating the feasibility of this design.
Fabrication and Evaluation of Devices Containing High K Gate Dielectrics and Metal Gate Electrodes for the 70 and 50NM Technology Nodes of ITRS
(2004-02-03) Suh, YouSeok; Dr. Carl Osburn, Committee Member; Dr. Veena Misra, Committee Chair; Dr. Gerald lucovsky, Committee Member; Dr. Gregory Parsons, Committee Member; Dr. John Hauser, Committee Member
This dissertation has focused on fabrication and characterization of alternative gate stacks consisting of high-K dielectrics and metal gates. This work has presented the evaluation of Ta based metals including Ta, TaNx, and TaSixNy as gate electrodes for their potential use in NMOS devices. For bulk CMOS devices, gate metals must have work functions that are near the conduction and valence band edges of Si. Although several metal gate electrodes have been identified for SiO2 dielectrics based on their work function, thermal stability and carrier concentration, their compatibility with high-K dielectrics is not fully understood. The questions that need to be addressed include thermal stability of metals on high-K, work function values, Fermi level pinning and performance. In this work, we report on the characteristics of metal gate electrodes on SiO2 and HfO2-based dielectrics with respect to equivalent oxide thickness (EOT), flatband voltage (VFB), leakage, work function and thermal stability. The research indicated that the workfunction of TaSixNy is compatible with NMOS devices, provided the right composition is achieved. The improved stability of TaSixNy gates is attributed to the presence of Si and N in the gate electrode, which can improve the film microstructure and the diffusion barrier properties at the gate-dielectric interface. This stability of TaSixNy films may enable high-k dielectrics and metallic electrode to be implemented in advanced CMOS devices. An equivalent oxide thickness of 11.2Å was obtained in TaSixNy /HfO2/p-Si MOS capacitor, while maintaining low leakage current density of 4.1 x 10-2A/cm2 at Vg-VFB=-1V in accumulation. A less EOT increase(~3 Å) was observed with TaSixNy gates compared to other gates (Ta, TaNx, and Ru) due to the excellent oxygen barrier properties of TaSixNy gates, preventing oxygen diffusion into the dielectric through gate electrode and dielectric during annealing. It was observed that trapped charge was increased with nitrogen sputtering ambient and interface charge density was increased due to bombardment damage during gate metal sputtering. Further optimization to reduce oxide charges in the dielectric would be necessary for advanced metal gate/high-k technology. Electrical characteristics of TaSixNy metal gate electrode on HfSiON/HfO2 gate dielectrics for N-MOSFET structure were also investigated. Capacitance-voltage results indicated that no evidence of gate-depletion with the introduction of TaSixNy metal gates. Reasonable output MOSFET characteristics such as Ids-Vgs, Ids-Vds, and Subthreshold swing, were obtained. However, degraded mobility characteristics were observed and were attributed to additional scattering mechanisms by trapped charges and interface charges in HfSiON/HfO2 dielectrics. A reduction in these charges is necessary to understand the intrinsic limitation of carrier mobility at Si-High-K dielectric interfaces.
Synthesis and Characterization of Nanoparticle Assemblies for Electronic Applications
(2009-07-27) Ayres, Jennifer Ann; Dr. Stefan Franzen, Committee Member; Dr. Edmond Bowden, Committee Member; Dr. Gregory Parsons, Committee Member; Dr. Christopher B. Gorman, Committee Chair
While significant effort has been made to synthesize molecular wires for electronic applications, the ability to insert these molecules between two metallic contacts with directional control has yet to be demonstrated. Control over molecular orientation is critical to the development of molecular devices such as diodes, capacitors and transistors. In this study, directional control is achieved using orthogonal self-assembly to synthesize electronic junctions between nanoparticles of different compositions. Phenyl ethynylene oligomers were synthesized with different end groups. One molecule was functionalized with a thiol which exhibits preferential binding to gold and an isocyanide which exhibits preferential binding to platinum. The other was functionalized with a thiol for binding to gold and a carboxylic acid which exhibits preferential binding to metal oxides. One of the major challenges of this work was the synthesis of nanoparticle building blocks that were suitable for the formation of these heterodimeric structures. Metal and metal oxide particles were synthesized with capping ligands that provided stability yet did not sterically hinder heterodimer formation. Once appropriate nanoparticles had been identified, preliminary studies indicated heterodimer formation. However, characterizing these structures presented additional challenges. Several characterization techniques, including transmission electron microscopy (TEM), size-exclusion chromatography (SEC), several types of electrophoresis and small-angle x-ray scattering (SAXS), were evaluated for their ability to characterize these structures with statistical accuracy. While all of these techniques did indicate the presence of dimers or larger aggregates in solution, accurate statistical information was not obtained using any single method.