All-carbocycle hydrocarbon thermosets with high thermal stability and robust mechanical strength for low-k interlayer dielectrics

Abstract

The development of the modern microelectronic industry calls for low permittivity interlayer dielectric materials with excellent thermal stabilities, robust mechanical strength and matching processability. Traditionally, it is difficult to fabricate materials with low k values, high heat endurance, high modulus and good processability simultaneously. Herein, we prepared two novel hydrocarbon precursors with dibenzocyclooctene (DBCOD) and thermo-crosslinkable benzocyclobutene (BCB) units by group transformation and cross-coupling reactions. These precursors can be cured at elevated temperatures to give crosslinked all-aliphatic/aromatic-ring structures. The low-polarizable hydrocarbon skeletons possess low dielectric constants (D_k = 2.66/2.54, respectively) and superior hydrophobicity (high water contact angle of ∼113°/125° and low water uptake of 0.10%/0.37%). Moreover, the rigid crosslinked cyclic structures render significantly high thermostability and mechanical modulus, such as very high glass transition temperatures (T_g > 380 °C/369 °C), high 5% weight loss temperatures (T_d,5% = 499 °C/492 °C), low coefficient of thermal expansion of 41.7/41.8 ppm K⁻¹, and storage modulus of 3.7/3.8 GPa, respectively. The enhanced comprehensive performances make the all-carbocycle hydrocarbon resins good candidates for next-generation interlayer dielectrics.