A low dielectric constant material synergized by calix[4]arene and benzocyclobutene units

Abstract

The rapid development of the semiconductor industry puts forward higher requirements on the properties of insulating dielectrics. As a supramolecular compound, calix[4]arene has a unique cavity structure, showing potential for a low-k material. We herein reported a novel strategy to functionalize the 4-tert-butylcalix[4]arene with different numbers of benzocyclobutene (BCB) units (2 or 4) and spacers (–(CH₂)₃– or –(CH₂)₆–) by sequential substitution and hydrosilylation reactions. These precursors can be cured under heating to form a crosslinked film. The optimized curation condition was screened by differential scanning calorimetry (DSC) measurement. Combining with a comparison experiment using a precursor with calix[4]arene but without BCB units, the wide-angle X-ray scattering (WAXS) pattern and thermal analysis provided solid evidence that the high thermal stability of the film (glass transition temperature (T_g) > 110 °C, 5 wt% loss temperature >367 °C, and the coefficient of the thermal expansion < 87.88 ppm °C⁻¹) was majorly contributed by calix[4]arene, while the excellent dielectric properties (the lowest dielectric constant D_k = 2.23 and the average dielectric loss D_f < 1.5 × 10⁻³) were synergistically affected by both calix[4]arene and BCB units. The static water contact angle was mostly higher than 100° and high hydrophobicity was confirmed, which can meet the additional requirements in practical application. The low dielectric constant synergized by calix[4]arene and the BCB unit is hoped to aid in developing a novel strategy for low-k materials.