No abstract

The electrodeposition of thin copper films on silicon substrates from copper pyrophosphate and copper sulfate solutions, without the addition of additives or hydrofluoric acid, is presented. The copper films obtained from these two solutions have different characteristics. Cyclic voltammetry was performed in order to investigate the silicon/electrolyte interface. This provides an explanation why the copper pyrophosphate solution is more favorable for electrodepositing copper on a semiconductor substrate. The copper films obtained with the pyrophosphate solution, having thicknesses ranging from 20 to 280 nm, were characterized in detail. They are homogeneous, exhibit a metallic luster, and show good adhesion. The topography was examined by atomic force microscopy, providing the root‐mean‐square roughness and the average grain size on the surface. The grain size values are compared with the average value of the scattering coherence length determined by X‐ray diffraction. The kinetic roughening of the copper deposits was investigated by dynamic scaling behavior and compared to previous studies. © 1999 The Electrochemical Society. All rights reserved.

The effect of electrolytic deposition parameters on the morphology of very thin (5 nm) copper layers was investigated by atomic force microscopy. Such thin copper layers were electrodeposited from solutions with different concentrations of copper sulfate and sulfuric acid on silicon wafers sputter-coated with a Ti layer and a Cu top layer. The characterization of these layers by atomic force microscopy shows that 5 nm thick Cu layers deposited by galvanostatic electrodeposition are homogeneous and present granular features on the surface. An increase of the copper sulfate concentration results in an increase in the size of the granular surface features. The lowest surface roughness is observed at a concentration of 100 g/L sulfuric acid.

A Co59 NMR experiment has been used to investigate the structure of two series of Co films with thicknesses varying from 5 to 400 nm which were electrodeposited on Cu at the electrolyte pH value of 2.1 and 3.7, respectively. It was shown that the overall structure of studied Co films consists of a very good quality fcc phase and a heavily faulted hcp phase in about equal proportions. The exceptions are very thin Co layers (below 20 nm) where the hcp structure was stabilized at pH 3.7 and overpotential of 0.9 V. This effect is attributed to the formation of hexagonal cobalt hydroxide in the early stage of deposition, which acts as a buffer layer stabilizing Co hcp structure.

We have studied the magnetic and structural properties of thin electrodeposited Co and Cu layers grown directly onto (100) n-GaAs and have investigated the influence of a buffer layer. A dominant fourfold anisotropy with a uniaxial contribution is observed in 10 nm Co electrodeposited films on GaAs. An easy axis is observed in the [001] GaAs direction with two hard axes of differing coercivities parallel to the [011] and [011] directions. For thicker films the easy axes in the [001] direction becomes less pronounced and the fourfold anisotropy becomes less dominant. Co films of similar thicknesses deposited onto an electrodeposited Cu buffer layer were nearly isotropic. From X-ray diffraction 21 nm Co layers on GaAs were found to be hcp with the c-axis tending to be in the plane of the film. The anisotropy is ascribed to the Co/GaAs interface and is held responsible for the unique spin-valve properties seen recently in electrodeposited Co/Cu films.