Morphologies, formation mechanisms, and mitigation strategies of groove-type scratches and ridge-type traces in slurry-less ECMP of 4H-SiC

4H-SiC wafers require damage-free, ultra-smooth surfaces for power devices manufacturing, whereas conventional chemical mechanical polishing (CMP) often suffers from limited throughput and high cost. Slurry-less electrochemical mechanical polishing (ECMP) enables efficient smoothing with low cost, but surface scratches still limit surface integrity and yield. This study systematically observed and classified surface morphologies formed on 4H-SiC under different ECMP conditions, including conventional groove-type scratches and ECMP-specific ridge-type traces, and elucidated the mechanisms underlying each type. Based on these insights, practical process-optimization strategies were proposed to suppress trace formation and improve slurry-less ECMP stability and applicability.