| Summary: | 碩士 === 國立虎尾科技大學 === 材料科學與綠色能源工程研究所 === 103 === Copper has been used as interconnects in ultra-large scale integrated (ULSI) because Cu has a high resistance to electromigration and high electrical conductivity. Generally, Cu interconnection needs a barrier to prevent Cu diffusion due to the fast diffusion of Cu into Si will introduce deep level traps. Furthermore, high-aspect trench/hole makes deposition of a conformal film more difficult as the device continuously scaling down. The Electrochemical atomic layer deposition (EC-ALD) used in this study is highly potential for application in Cu interconnection.
TaN (10 nm)/Ta (5 nm) thin films, as a barrier, were deposited on a silicon substrate by sputtering. Cu thin films were then deposited by EC-ALD. The first Cu seed layer was performed by underpotential deposition (UPD), and a layer of Pb was applied by UPD for use as a sacrificial layer. Finally, the next Cu monolayer was prepared by replacing Pb through a surface limited redox reaction (SLRR). The cycle was repeated 50 times to form a thick film. The sample was annealed at 300-800°C in Ar + H2 (95% + 5%) for 5 minutes. The resistance of the films was measured by four-points probe (FPP). The thickness of films was measured by surface profiler (α-step) and crystal structure was analyzed by X-ray diffraction (XRD). The surface morphology was observed by field-emission scanning electron microscope (FE-SEM) and the depth profiling was analyzed by Auger electron spectrometer (AES).
The results showed that optimal parameters can be obtained at UPD of Cu: -1100 mV, Pb: -1150 mV at a solution of pH 3.5. The lowest resistivity was 7.5 μΩ cm and the deposition rate was 1.09 ML/cycle for as-deposited film. The results showed that film is thermally stable up to 650 °C / 5 min.
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