Small-diameter TSV reveal process using direct Si/Cu grinding and metal contamination removal

We describe a through-silicon via (TSV) reveal process that uses direct Si/Cu grinding and metal contamination removal for the backside reveal of small-diameter (4 μm) TSVs. In this process, simultaneous grinding of Cu and Si was performed by using a novel grinding wheel (vitrified-bond type) and cleaning the grinding wheel with a high-pressure micro jet. Owing to the inelastic porous structure and in situ cleaning of the grinding wheel, the adhesion of Cu contaminants to Si was suppressed during grinding, and the TSVs could be leveled and revealed without burning and smearing of Cu. After this, electroless Ni-B plating was performed in order to prevent etching of Cu in the TSVs, and alkaline etching of Si was performed to reduce slight Cu contamination generated by direct Si/Cu grinding. As a result, TSVs were revealed uniformly and the K, Ni, and Cu contaminants in the Si region between TSVs were suppressed to below 5 × 10¹⁰ atoms/cm².