Backside Exposure of Small-Sized TSVs Using Si/Cu Grinding, CMP, Cap Layer Deposition, and Alkaline Etching

Abstract

For backside exposure of through-silicon vias (TSVs), we developed a new process using Si/Cu grinding, chemical mechanical polishing (CMP), cap layer deposition, and alkaline etching of Si. In this process, Si/Cu grinding without Cu burning or smearing was performed by using a novel grinding wheel (vitrified-bond type), with in situ cleaning of the grinding wheel by a high-pressure micro jet. CMP was then performed to remove grinding scratches generated by Si/Cu grinding. Next, slight Cu contamination in the Si region between TSVs was decreased by cap layer deposition and alkaline etching of Si. The cap layer was Ni-B film formed by electroless plating. We also applied the developed process to backside exposure of 4-μm-diameter TSVs. As a result, TSVs were exposed uniformly without grinding scratches and Cu contamination in Si region between TSVs was suppressed to < 2.7×1010 atoms/cm2.