STRUCTURES AND DIELECTRIC-PROPERTIES OF THIN POLYIMIDE FILMS WITH NANO-FOAM MORPHOLOGY

Thin polyimide films with dispersed nano-foam morphology have been pre pared for the purpose of obtaining low dielectric polymer insulators f or microelectronic applications. They were obtained by utilizing micro phase-separated triblock copolymers where the thermally stable polyim ide matrix component was derived from pyromellitic dianhydride (PMDA) with -bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3F) and a the rmally labile poly(propylene oxide)(PO) component comprised the outsid e block of the ABA triblock architecture. TEM studies show that the in itial irregular nanoscale phase-separated morphology of polyimide trib lock copolymers are mostly maintained in the final nano-foam films upo n thermal decomposition of the dispersed PO component. The nano-foam p olyimide films exhibit significantly lower dielectric constants epsilo n' (e.g., 2.3 at 19% porosity) as compared with epsilon'approximate to 2.9 for the homopolymer, as predicted by Maxwell-Garnett theory, with the nano-pore structures remaining stable at 350 degrees C. (C) 1996 American Institute of Physics.