In this study, the interface chemistry and adhesion strengths between Cu and SiCN etch stop layers have been investigated under different plasma treatments. From the examination of interface microstructures and the analyses of chemical compositions and bonding configurations, an oxide layer was found to exist at the untreated Cu/SiCN interface. After H-2 and NH3 treatments, the amount of oxides was effectively reduced. Some Cu silicides formed during SiCN deposition, and Cu nitrides even formed under NH3 plasma treatment. The adhesion strengths of the Cu/SiCN interfaces were measured by nanoindentation and nanoscratch tests under which interface delamination occurred around indented regions. The adhesion energy of the untreated Cu/SiCN interface was obtained as about 4.98 and 0.98 J/m(2), respectively, by nanoindentation and nanoscratch tests. After H-2 and NH3 plasma treatments, the adhesion energy was effectively improved to 5.90 and 5.99 J/m(2) by nanoindentation test, and to 1.74 and 2.58 J/m(2) by nanoscratch test, respectively, because of the removing of oxides and the formation of Cu silicides and nitrides at the Cu/SiCN interfaces. (c) 2007 The Electrochemical Society.