Physiochemical stability of copper/polyphenylquinoxaline interfaces

New results obtained with polyphenylquinoxaline (PPQ)/Cu multilayer structures are presented. Thermal stability at the Cu/polymer and polymer/Cu interfaces during the polymer curing process is very important to preserve good adhesion between the conductor and dielectric materials. The interfacial behavior is studied as a function of annealing temperature and of annealing atmosphere. In the case when copper is present, oxygen pollution, even at low levels, is shown to be detrimental for polymer integrity. Experimental results give a clear indication of catalytic degradation of the polymer in the presence of copper oxide. A thin chromium layer intervening between the Cu and polyphenylquinoxaline films is proven to be a very efficient oxygen diffusion barrier blocking any copper oxide formation and hence any enhanced polymer degradation