Abstract
The optimum electrodeposition conditions for via filling were obtained using the measurement of time-potential response. The result of time-potential response measurement corresponds well with the via cross section shape.
We adopted a two-step electrodeposition method. The first step is via filling by the periodic reverse pulse current of IOn/IRev/IOff=−20/40/0 [mA/cm2] and TOn/TRev/TOff=200/10/200 [ms]. Thirty minutes of periodic reverse pulse current perfectly fills a via of 40 μm in diameter and 25 μm in depth. The second step is etching by the periodic reverse pulse current of IOn/IRev/IOff=20/−40/0 [mA/cm2] and TOn/TRev/TOff=200/10/200 [ms], in order to uniformly etch the copper film on the via surface. Nine minutes was required to etch the copper film. Finally, the fine sized vias were perfectly filled and the uniform via surface of 6 to 7 μm was obtained within 39 minutes. With this thinner uniform via surface, it is easy to form fine wiring by the subtractive method.
