Electrochemical deposition of Cu and Ni/Cu multilayers in Si Microsystem Technologies

This work reports the microstructural and stress analysis of Cu layers and Ni/Cu multilayer structures grown onto Au (1 1 1) seed surfaces by EC processes that are developed for the fabrication of magnetic microactuator devices in Si technology. X-ray diffraction (XRD) measurements performed onto the electrochemically grown Cu layers has revealed the existence of a Cu/Au interface region with (1 1 1) texture and with a high tensile stress. Increasing the Cu layer thickness leads to a change of the preferential orientation of the Cu grains towards (2 2 0) texture, likely related to a stress relaxation. The Ni layers also show the coexistence of both (1 1 1) and (2 2 0) preferential orientations. In this case, the existence of an underlying Cu layer with dominant (2 2 0) texture leads to an enhancement in the (2 2 0) preferential orientation of the Ni grains. These layers are also characterised by the existence of high tensile stress levels, which, together with the high stress at the Cu/Au interficial region, lead to stress gradients, which might compromise the viability of the grown multilayer structures for microsystem applications.