Effects of Wet Chemical Treatment and Thermal Cycle Conditions on the Interfacial Adhesion Energy of Cu/SiNxthin Film Interfaces

Effects of wet chemical treatment and thermal cycle conditions on the quantitative interfacial adhesion energy of Cu/SiNx thin film interfaces were evaluated by 4-point bending test method. The test samples were cleaned by chemical treatment after Cu chemical-mechanical polishing (CMP). The thermal cycle test between Cu and SiNx capping layer was experimented at the temperature, -45 to 175 o C for 250 cycles. The measured interfacial adhesion energy increased from 10.57 to 14.87 J/m 2 after surface chemical treatment. After 250 thermal cycles, the interfacial adhesion energy decreased to 5.64 J/m 2 and 7.34 J/m 2 for without chemical treatment and with chemical treatment, respectively. The delaminated interfaces were confirmed as Cu/SiNx interface by using the scanning electron microscope and energy dispersive spectroscopy. From X-ray photoelectron spectroscopy analysis results, the relative Cu oxide amounts between SiNx and Cu decreased by chemical treatment and increased after thermal cycle. The thermal stress due to the mismatch of thermal expansion coefficient during thermal cycle seemed to weaken the Cu/SiNx interface adhesion, which led to increased CuO amounts at Cu film surface.