Wafer-Level Electrochemical Deposition and Processing of Nanotwinned Cu RDL

Abstract

We have successfully performed wafer-level ( 300 mm) fabrication of highly (111) oriented nanotwinned copper (nt-Cu) Redistribution layers (RDL) using through-resist electrochemical deposition on barrier/seed combinations such as TiW/Cu, TaN/Cu, and TaN/Ta/Cu. We have examined physical-chemical properties of nt-Cu and explored possible challenges in post-plating processing of these structures. After photoresist removal, nt-Cu lines were analyzed using Scanning electron microscopy (SEM) and Focused ion beam (FIB) techniques. Within wafer (WIW) and within die (WID) feature height uniformity were measured using profilometry and Cu losses in the plated lines upon wet-etch of the Cu seed were examined using automated SEM measurements.