HIGH-RESOLUTION PROFILING OF THE POLYIMIDE-POLYIMIDE INTERFACE

Dynamic secondary ion mass spectrometry (SIMS), nuclear reaction analy sis, and neutron reflectometry were used to profile polyimide-polyimid e interfaces. For interfaces between two layers of poly(4,4'-oxydiphen ylene-pyromellitimide) (PMDA-ODA) polyimide it was determined that the interfacial fracture energy G(c) and the interfacial width depended p rimarily upon the imide fraction, f, of the base layer. For f <0.9, th ere was a sharp interface between the deuterium-labeled poly(amic acid ethyl ester) (dPAE) and the base layer with a long low volume fractio n tail of dPAE penetrating into the base layer. The volume fraction of the penetrant was limited by the imide fraction of the base layer and approached zero for f > 0.9. The PMDA-ODA/PMDA-ODA interface formed w ith a fully imidized base layer was similar to 30 Angstrom in width, w hereas that formed when f = 0.9 was similar to 80 Angstrom in width. T he interface formed during the spin-casting process did not broaden si gnificantly after annealing at 400 degrees C. We also investigated the interface between a more flexible thermoplastic polyimide poly(4,4'-o xydiphenylene-oxydiphthalimide) (ODPA-ODA) and a fully imidized PMDA-O DA layer. The shape of the ODPA-ODA/PMDA-ODA interface was found to de pend upon annealing temperature. Unannealed samples and samples anneal ed at 350 degrees C could be fit with an error function, and the inter facial width was similar to 50 Angstrom. Samples annealed at 400 and 4 50 degrees C were best fit by a fairly sharp interfacial profile with ODPA-ODA tails proceeding into the PMDA-ODA layer. The volume fraction of the ODPA-ODA in the PMDA-ODA depended upon the annealing temperatu re T-ann. The G(c) of the ODPA-ODA/PMDA-ODA interface appears limited by the solubility of ODPA-ODA in PMDA-ODA.