Versatile Landscape of Low-k Polyimide: Theories, Synthesis, Synergistic Properties, and Industrial Integration

The development of microelectronics and large-scale intelligence nowadays promotes the integration, miniaturization, and multifunctionality of electronic and devices but also leads to the increment of signal transmission delays, crosstalk, and energy consumption. The exploitation of materials with low permittivity (low-k) is crucial for realizing innovations in microelectronics. However, due to the high permittivity of conventional interlayer dielectric material (k ∼ 4.0), it is difficult to meet the demands of current microelectronic technology development (k < 3.0). Organic dielectric materials have attracted much attention because of their relatively low permittivity owing to their low material density and low single bond polarization. Polyimide (PI) exhibits better application potential based on its well permittivity tunability (k = 1.1-3.2), high thermal stability (>500 °C), and mechanical property (modulus of elasticity up to 3.0-4.0 GPa). In this review, based on the synergistic relationship of dielectric parameters of materials, the development of nearly 20 years on low-k PI is thoroughly summarized. Moreover, process strategies for modifying low-k PI at the molecular level, multiphase recombination, and interface engineering are discussed exhaustively. The industrial application, technological challenges, and future development of low-k PI are also analyzed, which will provide meaningful guidance for the design and practical application of multifunctional low-k materials.