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 Si3N4/SiO2 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 SiO2 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 Si3N4 and SiO2 etching. The additives affected the etch rates of Si3N4 and SiO2 by changing the activation energies, thereby adjusting the etch selectivity. Additionally, the redeposited colloidal silica gel on SiO2 layers and the detrimental dissolution of poly-Si channel were characterized. These results will contribute to exploring solutions for challenges in 3D NAND manufacturing.