The Wafer Bonding yield improvement through control of SiCN Film composition and Cu Pad Shape

Wafer bonding of various dielectric films has been studied. Bonding strength is important for strong dielectric bonding. This bonding strength is directly related to not only electrical connections but also reliability issues during commercialization. The bonding strength of two SiCN films and TEOS films with different compositions in accordance with the type of plasma was studied. Bonding strength is closely related to the number of dangling bonds formed during plasma treatment on the film. Accordingly, controlling the elemental composition of the film to make more dangling bonds directly affects the quality of bonding. In accordance with the bonding strength of dielectric, wafer bonding with actual Cu pattern was carried out and electrical connectivity was confirmed. As a result, when O-2 plasma was used for a film with a high ratio of carbon elements among SiCN films, wafer bonding showed the highest yield. It was confirmed that nano gap was formed through linkage analysis of Electrical test, Emission, and cross-sectional analysis. In addition, we were able to secure a higher yield through an experiment to change the shape of the Cu pad in the optimized SiCN. We intentionally created a protruded and dishing Cu pad and performed Wafer bonding in various pad-shaped combinations. When evaluating bonding quality, the best results was showed when all of the upper and lower wafers have 3 to 5 nm dishing.