Understanding the ISPP Slope in Charge Trap Flash Memory and its Impact on 3-D NAND Scaling

We present a physical modeling approach that explains the non-ideal ISPP slope in charge trap layer (CTL) flash memory and its impact on 3-D NAND vertical pitch scaling. First, we derive an expression for the V-T change rate and use its field dependence to reproduce experimental vertical NAND ISPP slopes. Next, we implement a 2.5-D TCAD model based on these insights and show significant program voltage increase (>5V) in realistic 3-D NAND flash devices with scaling vertical pitch (down to lOnm). Finally, we evaluate high-k CTL and airgaps as mitigation measures at scaled pitch.

Automated summary

A physical modeling approach is presented to explain the non-ideal ISPP slope in charge trap layer (CTL) flash memory and its impact on 3-D NAND vertical pitch scaling. An expression for the V-T change rate is derived to reproduce experimental vertical NAND ISPP slopes, and a 2.5-D TCAD model is implemented to show significant program voltage increase in realistic 3-D NAND flash devices with scaling vertical pitch. Mitigation measures such as high-k CTL and airgaps are evaluated for scaled pitch.