Browsing by Subject "Electron beam"
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Item Advanced organic materials for lithographic applications(2010-08) Strahan, Jeffrey Ryan; Willson, C. G. (C. Grant), 1939-; Anslyn, Eric V.; Freeman, Benny D.; Iverson, Brent L.; Willets, Katherine A.The microelectronics industry is driven by the need to produce smaller transistors at lower costs, and this requires an ever-changing approach to the chemistry involved in their fabrication. While photolithography has been able to keep pace with Moore’s law over the past four decades, alternative patterning technologies are now receiving increased attention to keep up with market demand. The first project describes work towards increasing the sensitivity of electron-beam resists by incorporating electron-withdrawing groups into the alpha position of methacrylates. After monomer design and synthesis, several polymers were synthesized that investigated the role of fluorine in the resists performance. G-values, electron-beam contrast curves, and EUV imaging showed that these fluorinated polymethacrylates outperformed current industrial resists. The next project deals with the design, synthesis, and evaluation of a resist that seeks to decouple chemical amplification from acid diffusion. While work was shown that a system comprised of a photo-labile polyphthalaldehyde and x novolak could achieve this process, the high dose required to image was problematic. An aliphatic dialdehyde was envisioned to account for these issues, but its synthesis was never achieved. A polyethylene glycol aldehyde was synthesized and polymerized, but its material properties did not perform the intended function. Ultimately, the stability of aliphatic aldehydes proved to be too unstable for this project to continue. While the synthesis was troublesome, a fundamental study of ceiling temperatures was undertaken. Numerical and analytical solutions were developed that describe the exact nature of the equilibrium constant on a living polymer system. These results were verified by a VT-NMR experiment, which accurately predicted the ceiling temperature of polythalaldehyde with a Van’t Hoff plot. Lastly, the self-assembly of block copolymers was investigated as a means to produce high resolution, high density nano-imprint lithography templates for bit patterned media. The first set of experiments involved synthesizing polymeric cross-linked surface treatments from substituted styrenes. The aryl substituent was shown to largely effect the surface energy, and after anionically synthesizing PS-b-PMMA, these materials were shown to effect block copolymer orientation. To produce a 3-D pattern of the self-assembled features, silicon was incorporated into one block to provide adequate etch resistance. Several monomers were investigated, and two, an isoprene and methacrylate analog, were successfully incorporated into two block copolymers. The silicon containing methacrylate derivative polymer was shown to successfully self-assemble in thin films under solvent annealing conditions.Item Applications of neural networks in IC lithography(Texas Tech University, 1995-05) Mahendra, ManishaNot availableItem Electron Beam As A Next Generation Vaccine Platform: Microbiological And Immunological Characterization Of An Electron Beam Based Vaccine Against Salmonella Typhimurium(2014-04-16) Praveen, ChandniVaccines against infectious diseases are a corner stone of public health globally. Vaccine technology based on attenuation, conventionally ?killed? or cellular sub-units suffer from significant drawbacks. Live attenuated vaccines impart strong cellular and humoral immune response compared to inactivated or subunit vaccines, but there is an increased risk of infection from the potential virulence reversion in such formulations. The current study explores the use of eBeam irradiation as a novel tool for vaccine generation. The value of eBeam based vaccines is that, they combine the safety of ?killed? vaccines, yet retain the immunogenicity of ?attenuated? vaccines. The principle of eBeam vaccine is eBeam irradiation will only irreversibly damage the target microorganism?s nucleic acid without modifying the antigenic properties of surface macromolecules. In this study microbiological characterization of eBeam based S. Typhimurium (EBST) vaccine was carried out. The immunological correlates of protection induced by the EBST in dendritic cell (DC) (in vitro) and mice (in vivo) model were also assessed. Results showed that eBeam inactivation preserved the potent proinflammatory and immunogenic properties of S. Typhimurium. The EBST remained metabolically active yet unable to multiply under favorable in vitro and in vivo conditions. The EBST potently stimulated innate pro inflammatory response (TNF?) and maturation (MHC-II, CD40, CD80 and CD86) of DC. Immunostimulatory potential of EBST was on par with live Salmonella, and most importantly on par with a commercial Salmonella vaccine. Results from the mice challenge studies demonstrated the involvement of CD4+T cells as key player in cell mediated immune response of EBST immunized mice, triggering the production of Th1 cytokine IFN?. This indicates the stimulation and development of robust Salmonella specific T cell response similar to that caused by the live attenuated vaccine (AroA- ST) formulation. The colonization of virulent Salmonella was also reduced in EBST immunized mice similar to AroA immuninized mice. The EBST retained stable immunogenic properties for several months at room temperature, 4?C, - 20?C and also after lyophilization. These findings highlight the potential of eBeam technology as an effective and affordable next generation vaccine platform to address global public health issues.Item Evaluation of potential induced activity in medical devices sterilized with electron beam irradiation as a function of maximum electron energy(2010-12) Smith, Mark Anthony, 1956-; Biegalski, Steven R.; Landsberger, Sheldon; Schneider, Erich; Raizen, Mark; Hearnsberger, DavidCommercial sterilization of medical devices may be performed using electron beam irradiators, which operate at various electron energies. The potential for activating components of the devices has been discussed, with current standards stating that an electron energy greater than 10 MeV requires assessment of potential induced radioactivity. There does not appear to be a literature citation for this energy limit, but it is the accepted default assumption within the industry. This research was directed at evaluating potential activation in medical products sterilized in electron beam as a function of the electron maximum energy. Monte Carlo simulation of a surrogate medical device was used to calculate photon and neutron fields resulting from electron irradiation, which were used to calculate concentrations for several radionuclides. The predominant mechanism for inducing radioactivity is photoneutron production in metal elements. Other mechanisms, including photoneutron production in deuterium with subsequent neutron capture, neutron capture of the photoneutrons produced in metal elements, and isomeric excitation, are all possible means of inducing radioactivity in similar conditions, but none made a perceptible contribution to activation in these experiments. The experiments confirmed that 10 MeV is a conservative assumption that any lower energy does not create significant activation. However, in the absence of a limited number of elements, the amount of induced radioactivity at 11 MeV and 12 MeV could also be considered insignificant. When based on an estimate of the amount of metal present in a medical device, the sum-of-fractions comparison to the US Nuclear Regulatory Commission exempt concentration limits is less than unity for all energies below 12.1 MeV, which suggests that there is minimal probability of significant induced activity at energies above the generally-accepted standard 10 MeV upper energy limit.Item Synthesis and cure characterization of high temperature polymers for aerospace applications(Texas A&M University, 2006-04-12) Li, YuntaoThe E-beam curable BMI resin systems and phenylethynyl terminated AFR-PEPA-4 oligomer together with an imide model compound N-phenyl-[4-(phenylethynyl) phthalimide] were synthesized and characterized. E-beam exposure cannot propagate the polymerization of BMI system until the temperature goes up to 100oC. However, a small amount of oligomers may be generated from solid-state cure reaction under low E-beam intensity radiation. Higher intensity E-beam at 40 kGy per pass can give above 75% reaction conversion of BMI with thermal cure mechanism involved. NVP is a good reactive diluent for BMI resin. The cure extents of BMI/NVP increase with the increase of the dosage and applied dosage per pass. The reaction rate is much higher at the beginning of the E-beam cure and slows down after 2 dose passes due to diffusion control. Free radical initiator dicumyl peroxide can accelerate the reaction rate at the beginning of E-beam cure reaction but doesn??t affect final cure conversion very much. According to the results from FT-IR, 200 kGy total dosage E- beam exposure at 10 kGy per pass can give 70% reaction conversion of BMI/NVP with the temperature rise no more than 50oC. The product has a Tg of 180oC. The predicted ultimate Tg of cured AFR-PEPA-4 polyimide is found to be 437.2oC by simulation of DSC Tg as a function of cure. The activation energy of thermal cure reaction of AFR-PEPA-4 oligomer is 142.6 ?? 10.0 kJ/mol with the kinetic order of 1 when the reaction conversion is less than 80%. The kinetics analysis of the thermal cure of N-phenyl-[4-(phenylethynyl) phthalimide] was determined by FT-IR spectroscopy by following the absorbance of the phenylethynyl triple bond and conjugated bonds. The thermal crosslinking of N-phenyl-[4-(phenylethynyl) phthalimide] through phenylethynyl addition reaction has a reaction order of 0.95 and an activation energy of 173.5 ?? 8.2 kJ/mol. The conjugated bond addition reactions have a lower reaction order of 0.94 and lower activation energy (102.7 ?? 15.9 kJ/mol). The cure reaction of N-phenyl-[4-(phenylethynyl) phthalimide] can be described as a fast first-order reaction stage followed by a slow second stage that is kinetically controlled by diffusion.