Synergistic Crosslinking and Cage-Structured POSS Integrated in Polyimides: Toward Ultra-Low Dielectric Constant and High-Resolution Photolithography

Abstract

The increasing demand for high-speed and low-loss communication in the microelectronics industry has led to continuous efforts to develop interlayer dielectric materials with low dielectric constants. In this study, we developed photo-patternable polyimides (PIs) with low dielectric constants by constructing a micro-crosslinked architecture through an in situ thiol-yne click reaction between poly (amic acid) (PAA, precusor of PI) bearing alkynyl groups and thiol-functionalized polyhedral oligomeric silsesquioxane (POSS-SH). Remarkably, the covalent integration of POSS not only substantially improved the dielectric properties of the hybrid films by circumventing compatibility limitations but also maintained their mechanical robustness and thermal stability. This improvement is attributed to the unique hollow cage molecular structure of POSS, which mitigates inter-molecular charge transfer interactions and increases the volume fraction of nanopores within the hybrid films. At a doping level of 15%, optimal dielectric performance is achieved, with the dielectric constant and loss value reduced to as low as 2.21 and 0.0029, respectively, at a frequency of 10 GHz. Furthermore, through the incorporation of a photosensitizer, this resin demonstrates excellent potential for photolithographic applications of photosensitive polyimide (PSPI) plates,producing patterned structures with a resolution of 7 μm. This work presents an effective strategy to modulate the interactions between organic polyimide (PI) networks and inorganic nano-fillers, offering guidance for enhancing dielectric performance while maintaining other properties of PI. Additionally, efficient light-induced thiol-yne click reactions open new avenues for innovative exposure methods in PSPI materials.