ADHESION OF POLY(ARYLENE ETHER BENZIMIDAZOLE) TO COPPER AND POLYIMIDES

Poly(arylene ether benzimidazole) (PAEBI) is a high-performance thermo plastic polymer with imidazole functional groups which form the polyme r backbone structure. It is proposed that upon coating PAEBI onto a co pper substrate, the imidazole groups of PAEBI form a bond with or chel ate to the copper surface, resulting in strong adhesion between the po lymer and copper. The adhesion of PAEBI to other polymers such as poly (biphenyl dianhydride-p-phenylene diamine) (BPDA-PDA) and 6F photosens itive polyimide was also quite good and stable. The resulting locus of failure as studied by X-ray photoelectron and external reflectance in frared spectroscopy indicates that the failure is in the polyimide lay er for the case of polyimide/PAEBI/Cu adhesion. Owing to its good adhe sion and mechanical properties, PAEBI can be used in the fabrication o f thin film semiconductor packages such as multichip module dielectric (MCM-D) structures. In these applications, a thin PAEBI coating is ap plied directly to the wiring layer for enhancing adhesion to both the copper wiring and the polymer dielectric layer. In addition, a thin la yer of PAEBI can also function as a protection layer for the copper wi ring, eliminating the need for Cr or Ni barrier metals, and thus signi ficantly reducing the number of process steps. Once the PAEBI layer wa s spin applied onto the Cu and/or polyimide film, it was overcoated wi th a thick layer (similar or equal to 7 mu m) of BPDA-PDA polyimide. T EM analysis of the BPDA-PDA/PAEBI/Cu interface indicated that BPDA-PDA poly(amic acid) solution did not penetrate through a thin PAEBI layer . Applications of PAEBI to MCM packaging technologies, as well as the properties of PAEBI, are discussed.