This invention employs a novel approach to the copper metallization of a
workpiece, such as a semiconductor workpiece. In accordance with the
invention, an alkaline electrolytic copper bath is used to electroplate
copper onto a seed layer, electroplate copper directly onto a barrier
layer material, or enhance an ultra-thin copper seed layer which has been
deposited on the barrier layer using a deposition process such as PVD. The
resulting copper layer provides an excellent conformal copper coating that
fills trenches, vias, and other microstructures in the workpiece. When
used for seed layer enhancement, the resulting copper seed layer provide
an excellent conformal copper coating that allows the microstructures to
be filled with a copper layer having good uniformity using electrochemical
deposition techniques. Further, copper layers that are electroplated in
the disclosed manner exhibit low sheet resistance and are readily annealed
at low temperatures.
