Adhesion properties of polymethylsilsesquioxane based low dielectric constant materials by the modified edge lift-off test

Delamination occurring during the chemical and mechanical planarization process or wire bonding steps in packaging is a fundamental issue in integrating of low dielectric constant (low-k) materials into the multilayer structures of semiconductor chips. Since it is known that low adhesion strength is mainly attributed to the failure phenomenon, the measurement of interfacial fracture toughness is critical to provide a quantitative basis in the choice of the materials. In this study, a modified edge lift-off test was adopted to measure the fracture toughness of polymethylsilsesquioxane based low-k materials with various chemical and physical structures. Interfacial fracture toughness was improved by adding multi-functional monomers to methylsilsesquioxane monomers or by increasing the percentage of functional end groups inside the prepolymers. In addition, the change in curing conditions and thickness influenced the adhesion performance presumably by changing the morphology of low-k materials.