Monday, 9 November 2020

Micron Announces 176-Layer NAND, Volume Shipments Underway

Micron announced its 176-layer NAND flash today, and declared volume shipments to customers have already begun. This marks a new high-water point for commercial NAND density in absolute terms, and it will have a positive impact on the price of solid state storage in both the computing and the mobile phone markets.

Micron is claiming a number of firsts with this 5th Generation 3D NAND, including a 40 percent improvement in layer count, a 30 percent reduction in die size, a 35 percent reduction in write and read latency compared with Micron’s 96-layer NAND, and a 33 percent increase in raw data transfer rates. Micron may be comparing backward against its third-generation products because it didn’t widely commercialize its 4th generation hardware. Also, we should note that while Micron is claiming 176 layers of NAND, it’s getting that benefit from stacking two 88-layer stacks on top of each other. There’s nothing wrong with doing this, but it’s not the same thing as a single contiguous stack at 176 layers. A 176-layer contiguous stack is difficult to manufacture because the trench needs to be incredibly deep relative to its channel width. The more layers you stack, the harder it is to ensure uniform construction all the way to the bottom.

Micron’s 5th generation 3D NAND is also its 2nd-generation RG (Replacement Gate) implementation. According to Micron, replacement gate technology “significantly decreases the cell-to-cell capacitive coupling issues in traditional NAND that limit performance.” Traditional NAND relies on a floating gate-based architecture. Micron developed this alternate technology on its own.

Micron claims that RG offers higher endurance, increased power efficiency, improved storage capacities, and faster absolute performance. This new 176-layer NAND will give reviewers a chance to put some of these claims to the test, since 4th gen didn’t spend much time in-market. Micron’s whitepaper claims that RG NAND can write, read, and erase up to 2x faster than current 3D NAND.

It is not clear that we will see these performance benefits at the storage level, and I’m somewhat inclined to think we won’t. Micron’s press release and press briefing talk up its new 5th gen, 176-layer NAND as a major achievement in density and die size, but the company don’t claim a top-to-bottom performance realignment.

The physical differences between RG and traditional NAND. SiN stands for Silicon Nitride.

Between its use of CMOS Under Architecture (CUA, a method of placing control logic directly underneath the memory array) and its development of replacement gate, Micron is arguing that it’s stolen a march on other manufacturers. Customers are supposedly now able to buy products through the Crucial SSD line, but the company then states, “It will introduce new products based on this technology during calendar 2021” with no firm date attached. Since there’s no specific drive to announce today, it’ll obviously be a bit before we see this NAND in-market.

The collapse of NAND storage prices over the last decade has been a huge boon for mainstream computing performance. As NAND capacities continue to rise and consumers and businesses alike shift their purchases over to solid state hardware, the end result is faster performance for everyone, no matter what line of work you’re in.

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