Microfluidic Device for In Situ Observation of Bottom-Up Copper Electrodeposition in a TSV-Like Structure

Using a microfluidic device with a replica TSV (Through Silicon Via) structure, in situ observation of the copper via filling was made. Although the bottom-up TSV filling is possible by electroplating with a combination of several additives, the mechanism of bottom-up filling is not yet clear. Observation of the filling behavior is important, and cross sectioning of the TSVs is widely used. But the sectioning process takes some time, and continuous observation of the progress of deposition is difficult. In this study, a replica TSV structure was constructed in a microchannel, and real-time observation using the microfluidic device took place. As an example, extreme bottom-up filling obtained with addition of the leveler was monitored, and the effect of the immersion time before the plating, and progress of electrodeposition toward the via opening, were demonstrated. The observed deposition behavior was discussed in terms of the diffusion-adsorption model, and moderate agreement of the initial locations of deposition between the experiments and a simple 1-d numerical model estimate was obtained.