Investigation of Reducing Bow during High Aspect Ratio Trench Etching in 3D NAND Flash Memory
Ye Yuan, Zhiliang Xia, Li-Peng Liu, Zongliang Huo · 2018
One challenge of high aspect ratio etching in 3D NAND flash memory is to maintain the perpendicularity of the etching profile. In this paper, a method is proposed to reduce bow during high aspect ratio trench etching. Bottom critical dimension/top critical dimension (BT) ratio and bow critical dimension (CD) are two pivotal parameters. This work focuses on the etching of SiO2/SiNxtrench with aspect ratio larger than 50:1. By studying multiple influencing factors especially the function of different gas matching in every step, bow CD is improved while maintaining BT ratio in expectation.