Electroless-plated films have the desirable property of conformal deposition on dielectric under layers. Therefore, electroless plated (ELP) barrier metals are promising, for preventing Cu atom diffusion into SiO2 and Si in through-silicon vias (TSVs) used for three-dimensional (3D) integration. In this study, we evaluated Cu inter-diffusion properties after annealing at 400 °C for electroless-plated CoB and CoWB barrier layers with different W contents (0, 12.3, and 20.8%) formed on thin SiO2/Si substrate. The secondary ion mass spectrometry (SIMS) depth profile and cross-sectional TEM analysis of the TiN/Cu/ELP Co alloy/thin SiO2 (5 nm)/Si stacked films suggest that a CoWB film with a larger W content has a better effect on suppressing Cu inter-diffusion. It is demonstrated that ELP-CoWB having a large amount of W is a promising barrier layer for high-aspect TSVs used for 3D integration.

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