Hydrogen Source and Diffusion Path for Poly-Si Channel Passivation in Xtacking 3D NAND Flash Memory

Poly-Si channels need well passivated by using hydrogen passivation process in 3D NAND flash memories for better poly-Si quality with low trap density. It is believed that Xtacking 3D NAND flash memory has the advantage of flexible arranging the passivation process. In this article, two different passivation locations were compared in Xtacking structure to achieve better trap passivation. An optimized passivation process conducted at wafer backside with passivation SiN as hydrogen diffusion source was found to have an improved trap passivation result. This benefit was attributed to the sufficient H diffusion paths in Xtacking. These results also indicated the advantage of trap passivation for future higher stacked Xtacking 3D NAND flash memory.