| Title | "String-Stacking" Being Developed to Enable 3D NAND With More Than 100 Layers | |
| Date | Saturday May 28 2016, @05:13PM | |
| Author | martyb | |
| Topic | ||
| from the dense-memory dept. | ||
Tom's Hardware reports on a crude method that may enable the production of vertical/3D NAND with more than 100 layers in the future:
Today's 3D NAND weighs in at 32 to 48 layers, but increasing the density beyond 100 layers appears to be an impossible challenge due to the limitations of high-aspect ratio etch tools, which etch the holes in the NAND (1.8 billion for Samsung 48-layer NAND). Today's tools have 30:1 to 40:1 aspect ratios for 32- and 48-layer NAND, respectively, but creating 64-layer NAND will require an aspect ratio of 60:1 to 70:1. The only problem? There are no tools that can achieve that aspect ratio.
Several NAND vendors are reportedly developing a new "string-stacking" method that will merely stack the 3D NAND devices on top of each other. For instance, three 48-layer stacks will be stacked upon each other to create a 144-layer chip. String stacking may allow for scaling up to 300 layers, but the challenge will be how to link the stacks and produce it in a cost-effective manner. Unfortunately, the NAND fabs have not even mastered that for standard 3D NAND as of yet.
In other NAND news, there may be a shortage of 3D NAND, indicated by Samsung using 16nm 2D TLC NAND in its new 750 EVO SSDs.
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