The Role of Polycrystalline MoS₂ as Diffusion Barrier in Ru Interconnects: Thermal Stability and Electrical Performances

This study investigates the potential of polycrystalline MoS 2 as a diffusion barrier for Ru interconnects using in situ transmission electron microscopy (TEM) to assess its performance. By examining TEM diffraction and imaging, we evaluate the effectiveness of MoS 2 in suppressing interdiffusion, particularly focusing on the interactions and phase transformations between Ru and Si. When subjected to elevated temperatures, MoS 2 gradually loses its ability to block the interdiffusion, allowing Si to diffuse through the MoS 2 layer and form Ru 2 Si 3 within the Ru layer. Notably, plasma-treated polycrystalline MoS 2 (defective MoS 2 ) exhibits a slightly lower diffusion-blocking temperature of 700 °C, likely due to dangling bonds that improve interfacial adhesion. To complement our experimental observations, we performed density functional theory (DFT) calculations to compare Si diffusion in pristine and defective MoS 2 . Additionally, we assessed the electrical properties of Ru interconnects by measuring the resistivity and adhesion strength. These results underscore the considerable potential of polycrystalline MoS 2 even with defects as an effective diffusion barrier for Ru interconnects in semiconductor devices.