Synthesis And Application Of Nanoporous Polyimide Film

With the development of integrated circuits (ICs) industry, the quantity of transistors becomes much larger and the chip dimension becomes much smaller. The reduction in the electrical resistance induced by interaction between interconnected lines and the time delay caused by wire capacitance have become crucial problems limiting the progress of ICs. One of the strategies to meet these fast increasing requirements is to fabricate the insulator with low dielectric constant. According to ITRS 2009 the assigned value of the dielectric constant (k value) should be lower than 2.0 for the faster, smaller and higher performance ICs. However, the intrinsic k values of the most existing materials are much higher than this determined aim, so introducing air voids into low-k matrixes is expected to be the most attractive solution. However, most available porous polymer films cannot simultaneously meet the requirements of both low dielectric constant and good mechanical properties.In this work, the non-fluorinated PI derived from pyromellitic dianhydride (PMDA) and oxydianiline (ODA) was selected as the polymer matrix and the commercial triblock copolymer F127 (PEO106-PPO70-PEO106) as the template. Through a simple one-step solvent evaporation induced self-assembly (EISA) strategy, the PI films consisting of mesoporous nanoparticles (MPNPs) were produced. The influences of different F127 contents, end-capper and crosslinking agent in precursor, precursor molecular weight, solvent evaporation temperature, humidity, film casting type and template removal process on the structures and properties of resulting PI films were demonstrated. Moreover, a mechanism for the formation of MPNPs PI films was tentatively proposed. The characteristic results show that the diameters of the PI nanoparticles are less than 50 nm and the pore sizes inside particles are nanoscale. Both mesopores inside particles and voids among particles contributed to the porosity of the resultant PI films, making the lowest k value of MPNPs-PF as 1.92. Furthermore, the coalescent among the PI particles endowed the PI films relatively good mechanical properties, with modulus higher than 1 GPa.