Seedless electrodeposition of Cu thin films on ALD Ru diffusion barriers with different electrical properties

Abstract

Seedless Cu electrodeposition was performed directly on 10 nm atomic-layer-deposited (ALD) Ru diffusion barrier layer for Cu interconnect application in microelectronic devices. N2 gas flow rate ratio of Ru ALD process was varied between 0.24 and 0.86 to manipulate the electrical property of resultant ALD Ru layers. The nucleation and growth characteristic of Cu on ALD Ru changed depending on the electrical resistivity of ALD Ru layer under the potentiostatic deposition of Cu in an additive-free Cu-ammonia-citrate (Cu-NH3-Cit) electrolyte. As a result, a less resistive ALD Ru layer, which was formed at a lower N2 gas flow rate ratio, led to a lower electrical resistivity of Cu thin film.