Metallic Cu Ion Detection by Electrochemical Voltammetry of Interest to Post Cu CMP Cleaning

Abstract

After the Cu CMP process, many residues remain on the wafer such as slurry particle, organic residue and metal contaminants. Therefore, the surface is cleaned through the post-CMP cleaning process. However, during the cleaning process, Cu particles are generated and remain on the wafer or cause scratches. It is possible to prevent the occurrence of Cu particles by pre-investigating the amount of Cu ions generated during the process. The most common metal measuring method is ICP analysis, but due to the equipment size and measuring time, it is difficult to introduce into CMP equipment. In this study, it was confirmed that Cu ions easily converted into particles under alkaline conditions. Afterward, the Cu ions remaining on the wafer after the CMP process accumulate on the wafer surface or inside the PVA brush and turn into particles. As a proposed method, copper ions are detected by using anodic stripping voltammetry, a metal detection method that can be introduced into CMP equipment. Cu ions have been detected in various solutions and have been found to be usable in commercial cleaning solutions.