Fluorinated Parylene as an Interlayer Dielectric for Thin Film MCM's

Abstract

AbstractAliphatic tetrafluoro-poly-p-xylylene (PA-f), has been evaluated as an interlayer dielectric and its properties reported. It has a lower dielectric constant (2.38) and higher thermal stability (480°C) than Parylene-n. The as-deposited films are of very low crystallinity. The crystallinity increases as the film is annealed. Thermo-Gravimetric Analysis has shown that these films loose weight at temperatures > 480°C. A shrinkage in the films of about 10% was observed when annealed in vacuum at a temperature of 425°C. The as-deposited films were measured to have low dielectric constant of 2.38 and a volume resistivity of 1.3×1016 ohm-cm. The refractive index in the optical wavelengths was measured to be 1.3 for as-deposited samples which increased with anneal temperatures. The stress levels observed are also lower (19 MPa) than PA-n (40 MPa) after annealing. Diffusion of Cu into PA-f is comparable with Cu diffusion in PMDA-ODA polyimide. Scanning Electron Microscopy of film cross-section shows microstructure change above temperatures of 350°C.