A Novel Confined Nitride-Trapping Layer Device for 3D NAND Flash with Robust Retention Performances

For the first time, we've fabricated a confined nitride (SiN) trapping layer device for 3D NAND Flash and demonstrated excellent post-cycling retention performances. The key process step is to develop a uniform sidewall lateral recess in the 3D stack, followed by a SiN pull back process to isolate the SiN trapping layer in a self-aligned way. Excellent retention with only ~600mV shift of charge loss (out of initial 7V window) after 125C 1-week high-temp baking for a post 1K cycled device was obtained. It is far superior to the control sample without confined SiN structure. Arrhenius analysis at various baking temperatures shows that the retention may pass> 100 years at 60C, and is even longer at room temperature. The device has potential to meet the low-cost long-retention archive memory applications.