Nokia Bell Labs solves copper electroplating issues on seedless films

Nokia Bell Labs has published research detailing a method to overcome challenges in electroplating copper onto seedless barrier films, particularly addressing the effects of sheet resistance.

The study provides an analytical solution for understanding metal resistance-controlled plating current distribution on circular wafers. The findings indicate that uniform copper films cannot be deposited on 500 angstrom thick tantalum-based barrier layers on 200 mm wafers using conventional plating solutions, regardless of the plating current density.

Uniformity is characterized by a dimensionless polarization parameter, influenced by current density and material properties. The research suggests that by lowering the copper exchange current density in the plating bath by one to two orders of magnitude below common levels, a uniform, conformal conduction layer can be electro-deposited. This subsequently allows the bulk copper film to be plated at high rates.

Originally part of research published in 1999, this work offers a potential solution for improving semiconductor manufacturing processes, particularly in the creation of integrated circuits where copper is used for conductive pathways.