Atomic Layer Deposition Application in Interconnect Technology: From Material Understanding to Area Selective Deposition

Atomic layer deposition (ALD) technique has been widely employed in the semiconductor industry. As the devices continuously scaling down to sub 3 nm, SiOx and SiNx thin films, for applications such as a spacer or an etch stopper, are expected to satisfy stringent requirements (e.g., precise thickness control, high bulk film density, high wet-etch resistance, conformality, and lowthermal budget) in the current back-end-of-line process. Besides the film qualities, challenges in the current “top-down” approach also need to be addressed to reduce the size of the devices. Moreover, the lack of a fundamental understanding of surface chemistry using in-situ characterization can further impede future interconnect technology. This dissertation focuses on the application of the ALD process for current and future interconnect technology applications. The first study is ALD of high-quality SiOx and SiNx films with lowtemperature feasibility. With the structural modification of conventional Si precursors (e.g., the addition of ligand or substitution of terminating groups), the molecular polarity of precursors is changed, resulting in the improvement of surface reactivities. By leveraging the unique structure of the Si sources, the film deposition at low temperature with enhanced film properties can be achieved. Secondly, this dissertation further identifies the correlation between the metal surface condition and physical/chemical stability of passivation materials in application to the areaselective deposition process. Using in-situ reflectance absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), and high-resolution TEM analysis, the issues arising with poor ALD selectivity are identified. After analyzing the issues, the potential solution to provide a high-quality SAM monolayer is demonstrated. Lastly, a cleaning process using a noble metal cleaning agent, in which a clean metal surface at low temperature (< 200 o C) can be achieved, is developed. The unique cleaning process could pave the way for the implementation of the consecutive organic-free area-selective-deposition process.