Browsing by Subject "Diffusion barrier"

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Growth and characterization of amorphous ultrathin ruthenium metal films
(2017-08) Bost, Daniel Edgar; Ekerdt, John G.; Hwang, Gyeong S
Copper interconnect systems in modern microelectronics require the use of one or more liner layers and a capping layer in order to prevent copper diffusion into the other materials of the device. Ruthenium has been suggested as a replacement for the currently-standard Ta/TaN stack used for this purpose due to its low bulk diffusivity of copper and its good adhesion to both substrate materials and copper, but at very low thicknesses the polycrystalline nature of pure Ru allows for diffusion of copper along grain boundaries, resulting in the failure of the barrier. Because amorphous metal alloys do not form grains, amorphous Ru alloys have been examined as a way to eliminate the grain boundary diffusion of copper across the film. Early attempts to produce such films with phosphorus as an alloying element by chemical vapor deposition (CVD) using Ru₃(CO)₁₂ and organic phosphorus precursors such as trimethylphosphine have performed well relative to Ta/TaN as a barrier layer at 5 nm thickness. However, high concentrations of carbon were incorporated into the films during CVD by the P precursors. Carbon increases the resistivity of Ru(P) and adds an unnecessary element to the calculated structure of the amorphous alloy. To reduce resistivity, lower-carbon Ru(P) alloy films are grown at 250 °C using Ru₃(CO)₁₂ and a hydride gas (PH₃) as the P precursor. Diborane (B₂H₆) is used to grow an alternate alloy, Ru(B). Ru(P) and Ru(B) alloys are predicted by first-principles calculations to be amorphous above 20 at.% P for Ru(P) and 10 at.% B for Ru(B). Growth studies revealed amorphous Ru(P) above 17 at.% P and amorphous Ru(B) above 10 at.% B, with polycrystalline films formed at lower concentrations. Both Ru(P) and Ru(B) are found to deposit as smooth, continuous films at the 3 nm thickness. Metal-insulator-semiconductor (MIS) capacitor structures consisting of copper / amorphous alloy / SiO₂ / Si / Al stacks were used to test barrier performance under electrical stress. This testing confirms that the amorphous Ru films perform adequately as Cu diffusion barriers.
Investigation of the role of Fritz and its associated factors, septin and CCT in ciliogenesis of Xenopus laevis epidermis
(2014-05) Kim, Su Kyoung; Wallingford, John B.; De Lozanne, Arturo; Fischer, Janice; Gross, Jeffrey; Stevens, Scott
Cilia are evolutionarily conserved microtubule-based organelles projecting from nearly all vertebrate cells, and ciliary defects result in a variety of human disorders known as ciliopathies. Recent studies have shown that several planar cell polarity (PCP) proteins are essential for cilia functions. Here, we focused on Fritz, known as a novel PCP effector protein in Drosophila, in multi-ciliated cells in the epidermis of Xenopus laevis embryos. To investigate the role of Fritz, using confocal and scanning electron microscopy, we discovered that Fritz localizes along the ciliary axonemes and that knockdown of Fritz causes severe reductions in both axoneme length and number. Then, using pull-downs and mass-spectrometry, we identified Chaperonin Containing T-complex polypeptide 1 (CCT) and septin as interacting partners of Fritz. CCT is the key chaperonin interacting with septins, and both have been implicated in ciliogenesis. Using tagged CCT subunit constructs, we found that the tagged CCTα and CCTε co-localize with Fritz along the ciliary axonemes of multi-ciliated cells. Knockdown of Fritz resulted in the accumulation of CCT at the apical cytoplasm of multi-ciliated cells; however, it was confirmed that Fritz does not affect the CCT holoenzyme assembly. Septins, another interacting partner of Fritz, are novel cytoskeletal elements. Using septin antibodies, we found that endogenous septins also localize along the ciliary axonemes and accumulate in the apical cytoplasm of multi-ciliated cells in Fritz morphants. Similar ciliary defects were observed in septin morphants. Our results reveal that Fritz is essential for ciliogenesis, and that CCT and septin interact with Fritz to control ciliogenesis in Xenopus multi-ciliated cells. Additionally, tubulin acetylation is markedly reduced by Fritz knockdown, suggesting that Fritz affects tubulin acetylation.
Mitigation of the radioxenon memory effect in beta-gamma detector systems by deposition of thin film diffusion barriers on plastic scintillator
(2010-12) Fay, Alexander Gary; Biegalski, Steven R.; Haas, Derek
The significance of the radioxenon memory effect in the context of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty is introduced as motivation for the project. Existing work regarding xenon memory effect reduction and thin film diffusion barriers is surveyed. Experimental techniques for radioxenon production and exposure, as well as for thin film deposition on plastic by plasma enhanced chemical vapor deposition (PECVD), are detailed. A deposition rate of 76.5 nm min⁻¹ of SiO₂ is measured for specific PECVD parameters. Relative activity calculations show agreement within 5% between identically exposed samples counted on parallel detectors. Memory effect reductions of up to 59±1.8% for 900 nm SiO₂ films produced by plasma enhanced chemical vapor deposition and of up to 77±3.7% for 50 nm Al₂O₃ films produced by atomic layer deposition are shown. Future work is suggested for production of more effective diffusion barriers and expansion to testing in operational monitoring stations.