Chemical modification of polymeric surfaces to promote wettability and reactivity.

摘要

For the past few years, low-k dielectric polymers have had a major impact on the advanced integrate circuit technologies. Their potential use as interlayer dielectric combined with a low resistivity metal as the conducting line (e.g. copper) in interconnects can reduce the resistivity-capacity delay. However, in order to successfully integrate copper and low-k dielectrics for further use, it is first necessary to understand the interfacial interaction between copper and low-k dielectric.; This thesis work presents a systematic study with the primary goal of improving the polymer surface wettability and reactivity. Two hydrocarbon polymers, SiLK(TM) and Parylene, were used in this study, and the polymer surfaces were modified by either acid or plasma treatments. The change of surface morphology and surface chemistry due to the treatment was analyzed by atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS), respectively. A significant decrease of water droplet contact angle after the surface treatment reveals that the polymer surface wettability increases. It is found that the main factor in reducing the water droplet contact angle is the formation of oxygen and/or nitrogen functional groups on the polymer surface rather than an increase in the polymer surface roughness. The plasma treatment introduces a larger amount of functional groups onto the polymer surface than the acid treatment. The SiLK's crosslink structure is better withstanding the plasma force than the Parylene's linear polymer. Consequently, there are larger amounts of functional groups formed on the SILK surface than on the Parylenc surface.; An additional study reveals that the formation of functional groups on the polymer surface also increases the polymer surface reactivity and allows Tetrasulfide self-assembled monolayer growth on the treated polymer surfaces. The existence of functional groups and Tetrasulfide moiety markedly improves the copper interfacial interaction. It was observed that copper undergoes a reaction with oxygen functional groups, nitrogen functional groups and Tetrasulfide moiety. Further study of metallorganic Cu(hfac)2 adsorption indicates that the existence of functional groups on the plasma-treated polymer surface significantly enhances the Cu(hfac)2 chemisorption onto the polymer surface. The Cu(hfac)2 self-limiting growth behavior remains after it is adsorbed onto the polymer surface.