Selective Wet Etching Technology in 3D NAND Flash Manufacturing

3D NAND has become one of the most promising storage devices to meet the growing demand for large-capacity data storage. Stacking more Si
3
N
4
/SiO
2
layers in 3D NAND is essential for increasing its storage density. However, as the number of stacked layers increased, technical difficulties including poor etch selectivity, redeposition on SiO
2
layers, and dissolution of poly-Si channel arise in the wet etching process of 3D NAND manufacturing, seriously damaging the performance and reliability of the device. In this paper, we studied the kinetic effects of fluorine- and silane-containing additives on Si
3
N
4
and SiO
2
etching. The additives affected the etch rates of Si
3
N
4
and SiO
2
by changing the activation energies, thereby adjusting the etch selectivity. Additionally, the redeposited colloidal silica gel on SiO
2
layers and the detrimental dissolution of poly-Si channel were characterized. These results will contribute to exploring solutions for challenges in 3D NAND manufacturing.