Mechanical properties of copper micrometer pillars fabricated by intermittent MAGE process

A nano-universal testing machine (Nano-UTM) was used to investigate the mechanical properties of micrometer-sized copper pillars fabricated by the intermittent microanode guided electrodeposition (MAGE) process under various voltages (i.e., 2.8-3.0 V) and initial gaps (5-15 μm) between the electrodes. The Young's modulus, yield strength, fracture strength, and strain were deduced from the testing data, and their magnitudes were determined for the experimental conditions used with MAGE. The mechanical strength was higher for micropillars that were fabricated at lower voltages with greater initial separation (e.g., with the voltage at 2.8 V and initial gap at 15 μm) than those fabricated at higher voltages with smaller initial separation (e.g., with the voltage at 3.0 V and initial gap at 5 μm). After examining the surface morphology and transverse microstructure, we found that the stronger pillars revealed a smooth appearance with a dense internal microstructure, whereas the weaker pillars revealed a rough appearance with a porous internal microstructure. The fracture morphology was investigated to clarify the failure mechanism for various micrometer-sized copper pillars fabricated using the same MAGE process but under different conditions.