Controlled Directional Cu Outflow in Cu/W Nanomultilayers

Abstract

AbstractIn this study, we have investigated the feasibility of localized, focused ion beam (FIB)-stimulated Cu outflow in Cu/W nanomultilayers (NMLs) for manufacturing of heterogeneous micro-/nanojoints. Sub-micron-sized trenches were created on the nanomultilayer surface prior to heat treatment with the aim of directing the diffusion of Cu to locally defined NML surface regions. Cu outflow was triggered by annealing at 500 °C in a reducing atmosphere and lead to formation of (sub-)micron-sized Cu particles that are firmly joined to the W-terminated Cu/W NML. The results show that not only the depth of trenches (i.e., the parameters of the FIB treatment), but also the stress and the microstructure of the NMLs influence the Cu directional transport. The Cu outflow was found to be much more pronounced when the multilayer has a disordered microstructure with pores and open grain boundaries, as observed for NMLs with a tensile stress. We have thus demonstrated that FIB surface patterning enables the localized generation of (sub-)micron-sized Cu particles that can be used for manufacturing of micro-/nanojoints.