Advanced large-scale integrated interconnect structure faces a major challenge in forming a thin and conformal diffusion barrier layer. We deposited a Mn oxide layer by thermal chemical vapor deposition (CVD) on SiO2 substrates and investigated deposition behavior and diffusion barrier property. A thin Mn oxide layer was formed with a uniform thickness of 2.6–10nm depending on deposition temperature between 100 and 400°C. Heat-treated samples of Cu/CVD-Mn oxide/SiO2 indicated no interdiffusion at 400°C for 100h. The CVD of the Mn oxide layer was found to be an excellent barrier formation process.
A thin diffusion barrier was self-formed by annealing at an interface between a Cu-Mn alloy film and a SiO2 substrate. The growth of the barrier layer followed a logarithmic rate law, which represents field-enhanced growth mechanism in the early stage and self-limiting growth behavior in the late stage. The barrier layer was stable at 450 °C for 100 h and at 600 °C for 10 h. The interface diffusivity was estimated from the morphology change of the barrier layer at 600 °C and was found to be smaller than the grain-boundary diffusivity of bulk Cu.
A self-forming barrier process using Cu-Mn alloy has been reported to exhibit excellent reliability for interconnect lines in advanced semiconductor devices. However, Mn increases resistivity. In this work, the authors investigated optimum annealing conditions to remove Mn from the Cu-Mn alloy by forming an external Mn oxide and to reduce resistivity to a level of pure Cu. The results were interpreted by an external oxidation mechanism of Mn atoms.
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