An ultralow-k dielectric derived from a fluorinated polybenzoxazole composite film with yolk–multishell mesoporous silica nanostructures

Abstract

In order to solve the problem of signal delay and crosstalk caused by the miniaturization of VLSI circuits, it is urgently required to further reduce the dielectric constant (k) of materials. To date, porous low-dielectric materials still have shortcomings such as difficulty in controlling the pore volume and large fluctuation of k over a wide temperature range. Herein, a novel and controllable selective etching strategy to fabricate yolk–multishell mesoporous silica nanoparticles (YS-CSSs@3S-mSiO₂) is reported. This strategy allows precise control of the number of spherical shell layers, diameter, cavity size, mesoporous structure and core size, coupled with the closed-pore silica spheres (CSSs) as the core so that the obtained YS-CSSs@3S-mSiO₂ nanoparticles have a high pore volume (0.95 cm³ g⁻¹), low specific surface area (144 m² g⁻¹), uniform diameter and excellent monodispersity. We found that the corresponding 8 wt%-YS-CSSs@3S-mSiO₂/fluorinated polybenzoxazole (6FPBO) composite film possesses an ultralow dielectric constant (k = 1.87) that is very competitive among the low-k materials reported. Moreover, the nanocomposite films maintain great stability with almost unchanged k values over a wide temperature range up to 200 °C. The 5% weight loss temperature of nanocomposites reaches a maximum value of 540 °C. Accordingly, our current work provides a promising candidate for ultralow-k materials and lays a solid foundation for advanced material applications in the 5G communication and semiconductor field.