The use of copper interconnects enables higher speed, enhanced electromigration lifetime reliability, reduced power consumption, and ultimately reduced manufacturing cost for silicon integrated circuits. The formation of planarized inlaid copper interconnects requires sequential deposition of a continuous diffusion barrier layer followed by copper seed/fill deposition and chemical-mechanical polishing (CMP). In this article we present a vacuum-integrated cluster tool technology for deposition of a TaN barrier and copper seed/fill layers using metalorganic chemical vapor deposition (MOCVD). The MOCVD-based TaN layers deposited at substrate temperatures below 430 °C are highly conformal, have 800–1000 μΩ cm resistivity, have satisfactory adhesion to silicon dioxide, and provide superior diffusion barrier properties compared to Ta and TaN layers deposited by physical vapor deposition. The cluster MOCVD-Cu process is capable of depositing conformal and low-resistivity copper seed layers with satisfactory adhesion for subsequent copper filling by either electrochemical deposition or MOCVD. The cluster MOCVD technology has been used to fabricate inlaid copper metallization lines and plugs based on CMP damascene processing. The combination of MOCVD TaN and MOCVD copper is expected to provide an extendable multigenerational copper metallization solution for 0.18–0.10 μm technology nodes and beyond.
Background: Workers in hydroelectric plants appear to be readily sensitized to caddisfly allergens. This sensitization probably occurs de novo from occupational exposure. In some workers, sensitization occurs on a non-atopic background. Cytokine synthesis of IFN-γ, IL-5 and IL-13 in atopic and non-atopic caddisfly-allergic workers was examined to determine if responses were similar or different. Methods: Peripheral blood mononuclear cells were isolated from atopic caddisfly-allergic workers, non-atopic caddisfly-allergic workers and non-atopic caddisfly-exposed but non-allergic workers. Stimulation with caddisfly antigens was carried out and synthesis of IFN-γ, IL-5 and IL-13 was determined by sandwich ELISA. Results: Both caddisfly-allergic and non-allergic subjects responded to stimulation with caddisfly extract. The response in non-atopic caddisfly-non-allergic subjects was TH1 predominant, while that in atopic caddisfly-allergic subjects was TH2 predominant. The response in non-atopic caddisfly-allergic subjects was between that of the atopic caddisfly-allergic workers and the non-atopic caddisfly-non-allergic workers and the trend was to a TH2 response. Work-related symptoms were similarly intermediate between the atopic caddisfly-allergic and non-atopic caddisfly-non-allergic group. Differences were significant for IFN-γ/IL-5 ratios but not IFN-γ/IL-13 ratios for atopic and non-atopic caddisfly-allergic individuals, compared to non-atopic caddisfly-non-allergic workers. However, a linear relationship existed between IFN-γ synthesis and IL-5 and IL-13 synthesis in non-atopic caddisfly-allergic workers but not in atopic caddisfly-allergic subjects. Conclusions: Caddisfly allergy in hydroelectric workers may be a useful model for the development of allergy to a previously unencountered allergen, and points to some interesting differences between atopic and non-atopic subjects who become sensitized to environmental allergens.
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