| dc.description.abstract | Micrometer copper columns (roughly 50µm in diameter) were fabricated by a
patented process named as micro anode guided electroplating (MAGE). In this
process, a micro anode (made of Pt wire 125µm in diameter) was controlled to depart
from the cathode intermittently (1×1 cm2 silicon coated with 1.8µm copper) under
optimed biases to fabricate copper micro-columns in an acidic CuSO4 bath(CuSO4．
5H2O 200g/l，H2SO4 65g/l and 35g/l, HCl 1ml). The surface morphologies of the
copper micro columns, examined by scanning electron microscopy (SEM), depended
on the bias applied between the electrodes. The microcolumn obtained at a bias of
2.6V, displayed uniform diameter and smooth surface. In contrast, the micro column
fabricated at a bias of 3.2V was coralline and displayed rough surface. The sem
morphology of microcolumns was also influenced by the gap in each intermittent step.
A short gap (e.g. 1µm) led to nodose microcolumn with rough surface but a long gap
(e.g. 40µm) led to uniform microcolumn with smooth surface. The nodose
microcolumn exhibited a smaller diameter (1µm) than the uniform one (40µm).
Electrochemical impedance spectroscopy (EIS) was conducted to explore the MAGE
process. As the bias beyond 0.615V, the copper deposited. The range of bias from
0.615V(ocp) to 0.773V was the activation polarization of copper and 0.773V to 1.1V
was concerntration polarization. As the bias beyond 1.1V, the data of both C and Rp
decreased with increasing the bias, copper and hytroden found to deposition on the
substrate. In this work, practical range of bias was chosen from 2.6 to 3.2V because
the growth rate of the microcolumn was to slow under biases less than 2.6V, and
coralline microcolumn was not acceptable under biases greater than 3.2V. In
comparison with the microcolumns fabricated in various conditions, we obtained the
optimal conditions to attain the qualified copper microcolumns. The mechanism of the
MAGE process is discussed on bias of the EIS study. A row of four copper
micrometer columns was successfully fabricated. | en_US |