A Case of Plasma-Induced Film Breakdown in 3D NAND BEOL Dielectric Etch

In the latest 3D NAND product development, top via hole etch process is almost the last hole connecting process to complete a device fabrication. However, we encountered severe film damaged defects leading to a loss of over 30% in yield. Through a series of analyses, we uncovered the underlying root cause that relates to the presence of extensive metal defects embedded beneath the layer of inter-metal dielectric (IMD). As via hole etching down through IMD, unexpectedly arcing was happened because of overcharging onto these floating metal defects in plasma. This phenomenon has had a detrimental impact on process stability and yield. This paper comprehensively reports the mechanisms of defect formation and film breakdown damage on the structure. We also propose a solution to mitigate the problem and recover the yield effectively.