α α′ α″ α‴ Poly-tetrafluoro-p-xylylene as an interlayer dielectric for thin film multichip modules and integrated circuits

Abstract

α α′ α″ α‴ Poly-tetrafluoro-p-xylylene (PA-f ) has been evaluated as an interlayer dielectric for multichip modules and integrated circuits, and its properties are reported. It has a lower dielectric constant and higher thermal stability than parylene-n (PA-n). The as-deposited films have very low crystallinity. The crystallinity increases as the film is annealed. Thermogravimetric analysis has shown that these films lose weight at temperatures higher than 480 °C. A shrinkage in the films of ∼10% was observed when annealed in a vacuum at a temperature of 425 °C. The as-deposited film has a low dielectric constant of 2.38 and a volume resistivity of 1.3×1016 Ω cm. The refractive index at optical wavelengths was 1.3 for as-deposited samples and it increased with annealing temperature. The stress levels observed after annealing are also lower (20 MPa) than for PA-n (40 MPa). The hardness, as determined by a microindentor, of PA-f was 0.56 GPa in the bulk, but the surface hardness was ∼1.0 GPa. The conformal nature of these films permitted successful coating of micron-sized gaps having an aspect ratio of 1.5–2. Diffusion of Cu into PA-f is reported here and is contrasted with Cu/PMDA-ODA polyimide. Scanning electron microscopy of film cross sections shows microstructure changes above 350 °C. The low dielectric constant and high thermal stability of PA-f makes it a good insulator for high-speed interconnection applications.

Fast Electrically Switchable Capillary Effects

“…We found vacuum-deposited Parylene C to be a very useful coating material because of its high dielectric strength of about 200 V μm -1 . − Parylene can form conformal homogeneous coatings on surfaces of different shapes and compositions. Polyimide coatings on flat substrates also appear to have sufficient dielectric strength in water.…”

Partially ionized beam deposition of parylene

“…Due to their ability to form thin films that can conform to substrates of varied geometric shapes, parylene polymers are ideally suited for conformal coatings in a wide variety of fields [6]. Conformal coatings can serve as to protect electronic assemblies where high reliability and long switching life is required [7,8]. Parylene has also found its way into commercial and industrial uses because its material properties suit it to serve as a protective coating.…”

Poly(tetraflouro-p-xylylene), a low dielectric constant chemical vapor polymerized polymer

“…[2][3][4][5][6][7][8] Among the parylenes, ␣,␣,␣Ј,␣Ј poly͑tetrafluoro-p-xylylene͒ ͑AF-4͒ has the best properties. [9][10][11][12][13] However, currently the precursors for AF-4 are expensive and are not readily available. Therefore, a need exists to find new low dielectric constant materials whose precursors are inexpensive and readily available which produce a material satisfying the SEMATECH criteria for an intermetallic dielectric.…”