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

Abstract

This study investigates the potential of polycrystalline MoS₂ 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 MoS₂ in suppressing interdiffusion, particularly focusing on the interactions and phase transformations between Ru and Si. When subjected to elevated temperatures, MoS₂ gradually loses its ability to block the interdiffusion, allowing Si to diffuse through the MoS₂ layer and form Ru₂Si₃ within the Ru layer. Notably, plasma-treated polycrystalline MoS₂ (defective MoS₂) 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 MoS₂. Additionally, we assessed the electrical properties of Ru interconnects by measuring the resistivity and adhesion strength. These results underscore the considerable potential of polycrystalline MoS₂ even with defects as an effective diffusion barrier for Ru interconnects in semiconductor devices.