2 ms·
The whole reason why 3D NAND happened and higher layer counts enable cheaper, higher density storage is that it doesn't require an etch step per layer to build
by wtallis 1y ago
The whole reason why 3D NAND happened and higher layer counts enable cheaper, higher density storage is that it doesn't require an etch step per layer to build the memory cells. It's just deposit several dozen layers then etch holes down through all of those layers in one step, followed by filling in those holes with different materials. (Though at 276 layers, it's a stack of more than one deck of layers built as separate batches. The aspect ratio of the holes is the limiting factor.)
But aside from that, the cost of the NAND is the variable portion of the drive's cost, not part of the fixed floor of cost necessary for a drive of any capacity.
- HarHarVeryFunny 1y agoInteresting - thanks. I wasn't aware 3D NAND was built multiple layers at a time in this way. How are the layers made different, without individual masking and etch?
- wtallis 1y agoThe layers largely aren't different. The end result is a vertical string of (theoretically identical) NAND memory cells filling the holes that were etched through the stack, with contacts at the top and bottom. At the edge of the stack, at the end of the fabrication process, they etch a staircase to expose one contact with each layer. See https://thememoryguy.com/3d-nand-how-do-you-access-the-control-gates/ https://thememoryguy.com/3d-nand-how-do-you-access-the-contr...