Copper Metallisation of Barrier Materials

A study using SEM and AFM techniques was made of the electroless copper plating of barrier materials, TiN and W. The methods of plating TiN and W with a DMAB based copper bath are discussed. The morphology of the as-deposited copper on both substrates was examined using SEM firstly and then AFM for more detailed analysis of the barrier metal surfaces before and after plating. The topography of the copper plated TiN was attributed to the nucleation of the TiN surface with Pd prior to plating. Using AFM, it was found that the TiN surface consisted of a large scattering of oblong nodules. These nodules are the sites at which Pd seeds, and consequently the sites at which copper plating occurs preferentially. The surfaces of W and Cu plated W were also examined using AFM. It was found that the copper plated W surface was much rougher than the as-received W surface.