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 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 Fluorinated Polymethacrylates as Highly Sensitive Non-chemically Amplified E-beam Resists(2009-04) Strahan, Jeff R.; Adams, Jacob R.; Jen, Wei-Lun; Vanleenhove, Anja; Neikirk, Colin C.; Rochelle, Timothy; Gronheid, Roel; Willson, C. Grant; Strahan, Jeff R.; Adams, Jacob R.; Jen, Wei-Lun; Neikirk, Colin C.; Rochelle, Timothy; Willson, C. GrantIn an effort to improve upon the sensitivity of commercial non-chemically amplified e-beam resists, four polyacrylates functionalized with alpha-CF3 and/or CH2CF3 alkoxy substituents were studied. The alpha-CF3 substituent is known to increase backbone-scission efficiency while simultaneously eliminating acidic out-gassing and cross-linking known to occur in alpha-halogen substituted polyacrylates. Contrast curves for the polymeric alpha-CF3 acrylates, generated through e-beam exposure, showed the resists required an order of magnitude less dose than the current industry-standards, PMMA and ZEP. The fundamental sensitivity of these materials to backbone scissioning was determined via Co-60 gamma-ray irradiation. The chain scissioning, G(s), and cross-linking, G(x), values calculated from the resulting change in molecular weight demonstrated that all fluorinated resists possess higher G(s) values than either PMMA or ZEP and have no detectable G(x) values. Utilizing e-beam and EUV interference lithographies, the photospeed of PMTFMA was found to be 2.8x and 4.0x faster, respectively, than PMMA.