For years SanDisk has been presenting a memory roadmap (this post’s graphic is one rendition) that anticipates a move to ReRAM after 3D NAND has run through its natural life, which was expected to be as little as three generations. This has been backed by the idea that a 3D NAND stack would only be able to reach a certain number of layers before it would encounter difficulties caused by the need to etch a high aspect ratio hole through an increasing number of layers.
The aspect ratio issue is not hard to understand: Let’s assume that the hole in a 24-layer stack has an aspect ratio of 40:1, then a 32-layer hole would have an aspect ratio of about 50:1, and a 64-layer stack would be something close to 100:1. Today’s technology starts to have trouble etching holes with an aspect ratio higher than 60:1.
These high aspect ratios were thought to be the limiting factor that would prevent 3D NAND from continuing for more than three generations. 3D NAND could only have as many layers as the aspect ratio could support.
On a panel that I moderated at this year’s Flash Memory Summit one panelist, Dr. Myoung Kwan Cho of SK hynix, explained that although there is a limit Continue reading
A very unusual side effect of the move to 3D NAND will be the impact on the equipment market. 3D NAND takes the pressure off of lithographic steps and focuses more attention on deposition and etch. The reason for going to 3D is that it provides a path to higher density memories without requiring lithographic shrinks.
This sounds like bad news for stepper makers like ASML, Canon, and Nikon while it should be a boon to deposition and etch equipment makers like Applied Materials, Tokyo Electron, and Lam Research.
In its summer 2013 V-NAND announcement, Samsung explained that it would be Continue reading
Naturally, The Memory Guy fixated on those presentations that dealt with memory. When it came to the upcoming transition to 3D NAND, AMAT had a lot to say.
A later post will explain what 3D NAND actually is. Suffice it to say that today’s approach to making NAND flash has nearly reached its limit, and the approach that manufacturers plan to use in the future involves making NAND strings that stand on their ends. This has phenomenal implications on Continue reading