Multiphase imide block copolymers: new materials for microelectronics applications

Imide block copolymers were investigated as a means of lowering the dielectric constant and improving the polymer-polymer adhesion of poly(4,4´-oxydiphenylenepyromellitimide) (PMDA/ODA). Poly(perfluoroalkylenearyl ether) (PFAAE) was used as a coblock to introduce fluorine and lower the dielectric constant of PMDA/ODA. Poly(aryl ether-phenylquinoxaline) (PQE) coblocks were incorporated to improve polymer-polymer adhesion, since conventional poly(phenylquinoxalines) are known to be excellent hot melt adhesives. The preparation of imide copolymers required the use of poly(amic ester), rather than poly(amic acids), as the imide precursor. PFAAE and PQE were selected as coblocks due to their compatibility with the solvents required for the poly(amic ester) synthesis and processing as well as their excellent thermal stability and mechanical properties. The copolymers could be processed and cured with conventional techniques to afford high-quality coatings. The block copolymers showed excellent final properties, including high dimensional stability and tough, ductile mechanical properties. The materials displayed a heterogeneous morphology with submicron domains of PFAAE or PQE in a polyimide matrix. The PFAAE copolymers showed a reduction in dielectric constant relative to PMDA/ODA (ε≈2.8), and the copolymers of PMDA/ODA with ≈15-wt.% PQE showed excellent self-adhesion, as predicted