A Study of unique galvanic failure due to interaction with well structure

In this paper, a thorough investigation on a memory yield detractor due to metal void is presented. The metal void was found to have a strong dependency on isolated well size. It was formed due to galvanic effect. The failure mechanism in this unique case was found due to a potential developed from charges on the wafer surface and opposing charges trapped in the well. The post-etch solvent acted as the electrolyte and caused copper to migrate. This study includes a few counter-measures to address the issue.