New approach of local critical dimension uniformity improvement for via/contact hole etch with direct current superposition

As feature sizes continue to shrink for more advanced nodes, local critical dimension (CD) uniformity (LCDU) control becomes more critical than ever for improving defectivity, edge placement error, and yield enhancement. In this work, we developed a new approach utilizing an Ar plasma treatment with a direct current superposition function at low-temperature post patterning stack open. Our results demonstrated that this approach was capable of breaking the trade-off between CD shrink, LCDU improvement, and defectivity reduction. We significantly reduced the LCDU from 1.64 to 1.26 nm at the same CD level (∼10 nm). In contrast, no LCDU reduction was observed with the traditional CD shrink approach through trilayer process tuning. The mechanism for the LCDU improvement was investigated, and a hypothesis was proposed. We believe both the defect mitigation of the organic planarization layer profile and the vertical loading effect together with top sealing and in situ planarization contributed to the final LCDU improvement.