Compositional studies of near-room-temperature thermal CVD poly(chloro-p-xylylene)/SiO2 nanocomposites

Abstract.

Chemical-vapor-deposited (CVD) nanostructured thin films have been recently developed to overcome the limitations of thin films from one material class. In particular polymer/SiO₂ nanocomposite thin films have been developed to reduce power consumption, cross-talk, and RC delay in the next generation of ultralarge-scale integrated devices. Since polymers mainly possess electronic polarization they inherently have a low dielectric constant. However, they often suffer from poor dielectric anisotropy, low elastic and shear moduli, and have poor resistance to metallic diffusion. As a proof of concept, poly(chloro-p-xylylene)/SiO₂ thermal CVD nanocomposites have been developed to overcome such material deficiencies. Additionally, the CVD process allows for high manufacturing throughput and compositional control in situ, both potentially advantageous for IC fabrication. The study here focuses on the polymeric phase of the nanocomposite, which as a homopolymer can possess ≈60% crystallinity and a positive optical birefringence of 0.034, both post-deposition-annealed just before the polymer’s melting point. With increasing volume percent of SiO₂, the percent crystallinity is reduced, the thin film becomes more isotropic and the index of refraction can be varied depending on the volume percent SiO₂.