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In Situ Observation of Initial Nucleation and Growth of Chemical Vapor Deposition of Copper by Surface Reflectivity Measurement

Initial nucleation and growth of Cu thin films on a Ta substrate via chemical vapor deposition (Cu-CVD) for ultra large scale integration (ULSI) interconnects is monitored in situ by irradiating the substrate surface with 635-nm-wavelength laser light and then measuring the change in reflected-light intensity. The effect of injection of water vapor during deposition on initial nucleation and growth is investigated by using X-ray photoelectron spectroscopy (XPS) to measure the surface chemical state of the Ta substrate. Results show that water-vapor injection during Cu-CVD enhances both the nucleation and growth of Cu by introducing adsorbed OH groups onto the substrate surface and yields a smooth, continuous surface morphology. The optimal time at which to inject water vapor before and/or during deposition is also determined using our in situ monitoring technique.