Microstructure in electrodeposited copper layers; the role of the substrate

The microstructures of Cu layers, ranging in thickness from 3 to 12 microns, were investigated. The layers were electrodeposited from an acidic copper electrolyte onto two distinct substrate materials important for the micro-components industry: an Au layer with a pronounced lll-texture, and a nano-crystalline Ni-P layer. The evolutions of surface topography, morphology and crystallographic texture in the layers were investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction analysis, respectively. Distinct surface topographies were observed for Cu layers deposited on the Au and Ni-P substrates. Deposition onto the Au substrate resulted in a very smooth surface of Cu layers, whereas the Ni-P substrate caused an irregular surface for 3-microns-thick layers of Cu. The crystallographic texture in the Cu layers in the first few micrometres depended stongly on the crystallographic texture in the substrate. The Cu crystallites inherited the lll-orientation of the Au substrate, whilst no preferred crystallographic orientation was observed in the Cu crystallites on the nano-crystalline Ni-P substate. For Cu layers thicker than 3 microns a lll-fibre texture developed on both the substrates.