Double-decker silsesquioxane-doped benzocyclobutene functionalized siloxane polymer for low k materials

Benzocyclobutene (BCB) resins have been widely used in the microelectronics industry because of their excellent thermal, mechanical, and low k properties. In our previous work, we have prepared a BCB functionalized silphenylene-siloxane resin with good thermostability (Td5 > 490 °C in nitrogen). However, the dielectric constant of this BCB resin exceeds 2.8 and is expected to decrease. Herein, a linear BCB - functionalized polymer with a double-decker silsesquioxanes (DDSQ) doped silphenylene-siloxane backbone (DDSQ-PhBVSi) has been prepared using a Piers–Rubinsztajn reaction. It was cured at temperatures above 180 °C to obtain a thermoset. DDSQ with two reactive hydrosilyl groups is considered as a potential monomer to decrease the dielectric constant. The BCB group is introduced as a post-curing group to improve thermal and mechanical properties. Owing to the DDSQ units and the highly cross-linked structure, the thermoset exhibits a high initial storage modulus (>1.6 GPa at 25 °C) and good thermostability (Td5 > 495 °C in nitrogen). In addition, it exhibits good dielectric properties with a low k (2.69) and a low dissipation factor (<0.001) at 1 MHz.