Low Dielectric Poly(imide siloxane) Films Enabled by a Well-Defined Disiloxane-Linked Alkyl Diamine

This paper presents an efficient pathway to achieve the dielectric constant as low as 2.48 @ 25 °C, 1 MHz for nonporous poly(imide siloxane) films with mechanical and thermal robustness. A symmetric disiloxane-linked alkyl diamine, bis(aminopropyl)tetramethyldisiloxane (BATMS) with a well-defined molecular formula NH₂CH₂CH₂CH₂Si(CH₃)₂OSi(CH₃)₂CH₂CH₂CH₂NH₂, has been used to controllably reduce the dielectric constant of the polymer films by adjusting the loading of BATMS. The thermal stability of all the polymer films remains robust with T ₅ and T ₁₀ no less than 458 and 472 °C, respectively, while the glass-transition temperature decreases with increasing incorporation of flexible disiloxane-alkyl segments into a polymer backbone. There exists a consistent regularity between the thermal, optical, and dielectric properties with the loading amount of BATMS in the polymer films, inferring that the disiloxane-alkyl segments are homogeneously distributed in the polymer backbone. Charge-transfer complex inhibition of polymer films by disiloxane segments has been revealed by an enlarged d-spacing in wide-angle X-ray diffraction spectra and a blue shift in film fluorescence emission spectra. The combined low dielectric constant, robust mechanical and thermal stability, and improved hydrophobicity make the series of BATMS-resulting poly(imide siloxane) films promising candidates for sophisticated flexible microelectronic application.