Synthesis and characterization of low‐dielectric photosensitive polyimide/silica hybrid materials

Photosensitive polyimide/silica hybrid materials were synthesized by reaction between 4,4′‐hexafluoroisopropylidene diphthalic anhydride (6FDA) and 4,4′‐oxydianiline. The intrachain chemical bonding and the interchain hydrogen bonding between the polyimide and silica moieties were increased by the incorporation of 2‐(dimethylamino) ethyl acrylate and 3‐aminopropyl trimetho xysilane, respectively. The photoinitiator was bis(2,4,6‐trimethyl benzoyl) phenylphosphine oxide (Irgacure‐819). The various coupling agents were utilized included tetrakis (allyloxy) silane (TAL). Most silica hybrid films showed better volume shrinkage and temperature resistance. The cooperation of octavinyl POSS, as the coupling agent, can lower dielectric constant ( k ) down to 2.48 but with the poorer volume shrinkage and temperature resistance than the other silica hybrid films. The addition of tetramethyl orthosilicate and 3‐methacryloxy propyltrimethoxysilane with silica content of 5.6 wt % can reduce k down to 2.26 but with worse volume shrinkage than the incorporation with TAL. The TAL hybrid film with degree of polymerization of 25 showed the best properties that optimized photolithography, dielectric constant ( k = 3.81), volume shrinkage, and temperature resistance (Td5% = 378°C) with only 0.22 wt % silica content.