Determination of adhesive fracture energy from quasi static debonding of thin films

The adhesion of thin films is becoming increasingly important in microelectronics devices. The range of materials and surface treatments that are becoming available are increasing rapidly and their effect on bond strength and durability needs to be determined in a manner that not only ranks different processing routes and materials but also provides quantitative data that can be used in durability analyses.; The purpose of this work was to develop techniques for determining the adhesive fracture energy of thin films bonded to rigid substrates.; The stress levels and extent of yielding in various types of blister tests were compared on the basis of nonlinear von Karman plate theory and linearly elastic material behavior. These analyses of stationary cracks indicated that the peninsula blister configuration was the most promising. However, obtaining suitable specimens became a problem and attention was focused on circular blister specimens of polyimide on aluminum.; A series of experiments was conducted on specimens with different surface treatments. Extensive yielding was observed in all cases. Several approaches for extracting the adhesive fracture energy in the presence of global plastic dissipation were considered. The most promising was an embedded fracture process zone approach that allowed quasi static crack growth to be analyzed and global plastic dissipation to be extracted.; The adhesive fracture energies of the different surface treatments were compared with spectroscopic analyses of pre and post cured interfaces and fracture surfaces. The formation of carboxylate species in some of the treatments was considered responsible for the formation of a weak interphase region.