Thickness dependence of morphology and mechanical properties of on-wafer low-k PTFE dielectric films

The structure and morphology of on-wafer low-k ultrathin dielectric polytetrafluoroethylene (PTFE) films have been investigated using X-ray diffraction (XRD), polarized optical microscopy (POM) and scanning electron microscopy (SEM). The morphology observed by POM and SEM is found to be thickness-dependent; the characters of spherulite and lamella morphologies became mature gradually with increasing thickness. A similar thickness dependence of spherulitic and lamellar morphologies is found. The thickness-dependent Young's modulus and hardness obtained by the dynamic contact module (DCM) in a unique frequency-specific depth-sensing indentation can be explained by the observed thickness dependence of morphology.