Fundamentals and improvements of diffusion barrier/copper adhesion for damascene process

Abstract

Surface chemical and physical modifications of copper were performed to improve the adhesion of dielectrics on copper. The topography change of copper surface and formation of chemical bonding were revealed by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), attenuate total reflectance Fourier-transform infrared spectroscopy (ATRFTIR) and grazing angle FTIR. Modified edge liftoff tester (m-ELT) was used to measure the adhesion strength. Oxygen and nitrogen plasma treatments on copper were found to greatly enhance the copper-to-barrier adhesion. The examination of two major adhesion theories, mechanical interlocking mechanism and chemical bonding interaction, has shown that the chemical bonding is a dominant interaction for the adhesion of dielectrics on copper. The fundamentals of adhesion and spectroscopic evidences of new chemical bonding formation in the copper-to-barrier interface were also discussed in this article.