Ultralow Dielectric Constant Films from the Polyisoprene Modified with Dual Functions of Benzocyclobutene and Vinyl Groups

The rapid advancement of the semiconductor industry has imposed heightened demands on interlayer insulating dielectric materials to meet varying processing requirements. In this contribution, a series of polyolefin-based low-k materials were developed by integrating dual functional groups of benzocyclobutene (BCB) and vinyl together through grafting the BCB group onto the polyisoprene (PI) mainchain. As a comparison, the PI mainchain was also selectively modified as a hydrogenated PI (HPI) counterpart. Both the introduced BCB and the remaining vinyl groups on PI could be selectively cured at 250 and 360 °C, respectively. Notably, with the increase of BCB group contents, the storage moduli, tan δ, and glass transition temperature (Tg) of the cured samples were regularly enhanced, and the coefficients of thermal expansion (CTE) values were correspondingly decreased. Especially, by modulating the curing behavior of BCB and/or vinyl groups, the Tgs could be tailored across a broad range (29 to 240 °C), ensuring adaptability to diverse processing conditions. As expected, the polyolefin-based materials exhibit exceptional dielectric performance with all film samples demonstrating a dielectric constant (Dk) < 2.5 and dielectric loss (Df) < 5 × 10–3 (at 1 MHz). This work illustrated that the PI modified with dual functions of BCB and vinyl groups possessed significant potential as a low-k material for future versatile, integrated circuit applications.