Vapor phase infiltration of aluminum oxide into benzocyclobutene-based polymer dielectrics to increase adhesion strength to thin film metal interconnects

Interfacial adhesion between metallic thin films and polymers is a critical performance metric for a number of microelectronics and packaging applications. Delamination of metal-polymer interfaces is a frequent failure mode for many multilayer structures, like those used for electronics packaging. Such a failure is even more likely when electronic packages are operated under extreme conditions like high-power, high-temperature, and/or high-humidity operation. Roughening or direct chemical modification of the few layers of atoms that make up the interface is often used to promote adhesion at these interfaces. Here, the authors investigate a new process, vapor phase infiltration, that infiltrates inorganic constituents into the bulk of the polymer, creating an interpenetrating network within the subsurface of the polymer that further enhances interfacial adhesion. For the authors' model system of copper films on a benzocyclobutene polymer, they are able to increase the interfacial adhesion strength by as much as 3x, resulting in cohesive rather than adhesive failure. The authors attribute this increased interfacial adhesion to physicochemical interlocking of the organic and inorganic phases within the subsurface of the polymer, generating a "root system" that impedes interfacial delamination.