Sequential observation of electroless copper deposition via noncontact atomic force microscopy

Abstract

The dynamic morphological evolution of electroless copper deposition on palladium-activated high density physical vapor deposited TiN and oxide passivated TiN has been studied via noncontact atomic force microscopy. With precise control of the vibrational amplitude and resonant frequency of the cantilever probe, submicrometer length scale images were sequentially acquired for the deposition process. The different substrates are associated with two different growth schemes, although in both cases, lateral growth across the substrate dominated over vertical growth during the initial nucleation stage, which was followed by three-dimensional growth. In the case of TiN, simultaneous nucleation of Cu nodules on Pd nucleation catalyst and TiN grains was observed in the initial nucleation stages. However, only deposition of Cu grains on Pd catalyst was found in the case of oxide passivated TiN. Nevertheless, both growth schemes eventually lead to the formation of continuous Cu films.