A Multi-Scale Simulation Study of the Structural Integrity of Damascene Interconnects in Advanced Technology Nodes

The structural stability of damascene inter- connects for back-end-of-line (BEOL) technologies is an- alyzed using a combination of force-field based molecu- lar dynamics simulations and finite-element modeling. The candidate metals analyzed are- ruthenium, cobalt, tung- sten, and copper. Cohesive traction and normal bonding energy are calculated using force-field based molecular dynamics simulations and then fed as input to a finite- element analysis (FEA) tool, where their dependence on physical dimensions of the interconnect lines is studied. The characteristics of these metals are compared against the characteristics of copper. The parameters studied for the BEOL structures are sidewall angle, aspect ratio, inter- nal stress of the metal, and modulus of elasticity of the di- electric material around the metal at 18 nm pitch. Generally, lower aspect ratio and higher modulus of elasticity of the dielectric results in structures that show a lower tendency to collapse. Intrinsic stress of the metal and side wall angle have a minor impact on the overall stability. Based on this study, cobalt is most stable alternate metal amongst Ru, Co, and W.