Effects of surface treatments for the adhesion improvement between Cu and SiCN in BEOL interconnect

This study focuses on the enhancement of interfacial reliability between Cu interconnects and silicon carbon nitride (SiCN) capping layers in semiconductor packaging structures through pre-deposition surface treatments. We compare three distinct treatments combined with H₂ plasma, NH₃ plasma, and SiH₄ gas inflow, evaluating their effectiveness through quantitative measurement of interfacial adhesion energy using a double cantilever beam (DCB) fracture mechanics test. The results exhibit a remarkable adhesion energy improvement of over 1150 % with the addition of SiH₄ gas treatment. Thorough investigations reveal that the mechanism of the exceptional adhesion enhancement is attributed to unique chemical bonding and fracture behavior. In other words, Si atoms in the SiH₄ gas treatment incorporate onto Cu surfaces with specific crystallographic orientations, resulting in significantly stronger Cu–Si bonding in selective regions compared to other bondings. Moreover, the crystallographic-orientation-dependent bonding characteristic induces crack kinking at grain boundaries, dissipating the crack propagation energy. This work will provide crucial insight into enhancing the interfacial reliability and manufacturing yield of semiconductor devices.