Line Edge Roughness Reduction in High Aspect Ratio Carbon Hardmask Patterning for Slit Trench

The amorphous carbon used as the hard mask for the etching of slit trench in flash memory, was etched using O2/COS and pulsed dual-frequency inductively coupled plasma. Line edge roughness(LER) of carbon hard mask will transfer to slit trench and result in severe yield loss. In this paper, lots of methods are proposed to reduce LER. The results show that LER can be significantly improved by reducing deposition, lower bias power and enough time or plasma amounts to remove sidewall polymer.