Pore orientation and silylation effects on mesoporous silica film properties

Low dielectric permittivity mesoporous silica (MPS) films with high mechanical and chemical stability are attractive for electrically isolating multilevel wiring in future nanodevices. Here, we show that pore structure is a crucial determinant of chemically induced leakage currents in pristine and silylated MPS films and strongly influences film stiffness and hardness in silylated MPS films. Films with three-dimensional pore networks exhibit superior mechanical properties than films with cylindrical pores oriented exclusively parallel to the surface. The latter, however, exhibit a fourfold higher resilience to copper diffusion. These differences are attributed to the pore structure and its influence on silylation-induced bond-breaking and passivation.