Impact of Patterning Technique on the Long Term Stability of Ag Thin Films

With rising demand for high power electronics, the need for metallization systems with enhanced electromigration resistance increases rapidly. The long term stability of sputter deposited silver thin films is investigated with samples patterned either by wet chemical etching or by a lift-off process. Five conductor lines connected in parallel are stressed simultaneously by high temperatures and current densities. Whereas the activation energy is similar for both structures due to the same material system, the mean time to failure differs substantially because of a porous edge morphology occurring only at wet etched structures. Therefore, the current distribution is inhomogeneous thus, resulting in a significant faster failure of single conductor lines.