Mechanical Properties, Fracture and Water Diffusion in Nanoporous Low Dielectric Constant Materials

Extendibility of Cu/Low-k integration schemes beyond the 45 nm node requires integration of nanoporous dielectrics with greatly reduced permittivity into the back-end process of integrated circuits (IC). However, existing candidate materials suffer insufficient mechanical integrity and fracture resistance to survive the harsh fabrication flow. Their open pore structure is susceptible to the ingress of various detrimental chemicals during processing. In this work, we investigate these critical challenges that the industry confronts. In chapter 3, the intrinsic effect of porosity on the stiffness and fracture toughness are modeled by first separating out effects caused by difference in the matrix material at different levels of porosity, and by then comparing with finite element calculations and physical models. It is demonstrated that the fracture energy of porous organosilicate glasses (OSG) is largely determined by the porosity only. However, the elastic stiffness depends on both porosity and the morphology of the porous structure. Chapter 4 provides quantitative guidelines for the bottom-up design of new organosilicate materials with high modulus and low dielectric constant. Atomistic simulations are