New Approach of LCDU Improvement for Via/Contact Hole Etch at Cryogenic Temperature

Abstract

As feature sizes continue to shrink for more advanced nodes, local CD uniformity (LCDU) control becomes more critical than ever for improving defectivity, edge placement error (EPE), and yield enhancement. In this work, we developed a new approach utilizing an Ar plasma treatment with direct current superposition (DCS) function at cryogenic 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. Compared to the baseline condition, we significantly reduced the LCDU from 1.7 nm 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 tri-layer process tuning. The mechanism for the LCDU improvement was investigated and a hypothesis was proposed. We believe both the defect mitigation of OPL profile and the vertical loading effect together with top sealing and in-situ planarization contributed to the final LCDU improvement.