Development of Cu-less TSV reveal process using Si/Cu grinding, electroless Ni plating, and alkaline etching of Si

We developed a novel through silicon via (TSV) reveal process using Si/Cu grinding, electroless Ni plating, and alkaline etching of Si. For simultaneously grinding Cu and Si without the Cu burning and smearing, a vitrified-bond grinding wheel was used. To avoid Cu contamination during the alkaline etching of Si, electroless Ni plating was performed. We also investigated Cu contamination in the Si region between TSVs after this process. The investigation was carried out using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and dynamic SIMS. The results showed that the developed process enabled the leveling of TSVs and suppressed the concentration of Cu contaminants to 10¹¹ atoms/cm².