The NAND flash memory market is also feeling the impact of this trend, driven by the demand for high-bandwidth storage (HBM) in artificial intelligence (AI)-related semiconductors. Recently, Kioxia outlined 1,000 layers of 3D at the IWM 2024 conference in Seoul NAND's technology roadmap. And it is predicted that by 2027, the density of NAND chips will reach 100 Gbit/mm2 with 1,000 word line (memory cell) layers.

What does a higher layer of NAND bring?

The higher the number of layers stacked in a NAND chip, the main performance benefits include increased storage density, improved read and write speeds, improved input and output efficiency, reduced power consumption, and reduced physical footprint. This set of benefits is especially important for products such as miniaturized, high-performance mobile devices and solid-state drives (SSDs).

For the NAND industry, NAND flash storage itself is in the AI ecological chain, and any data cannot run without SSD, so the rise of large models will objectively trigger the demand for NAND.

As the number of stacks increases, there is no doubt that capacity will increase and cost per unit will decrease, and with it, the price of SSDs will also drop.

1000 floors are not necessarily the end

3D The number of NAND layers has generally increased from 24 in 2014 to 238 in 2022, a tenfold increase in eight years. Kioxia says it will reach 1,000 floors by 2027 at a growth rate of 1.33 times per year.

Increasing the number of active layers in a 3D NAND device is the best way to increase the density of flash recordings today, so all 3D NAND manufacturers strive to achieve this goal by introducing new process nodes every 1.5 to 2 years. Although the current competition is mainly focused on about 200 layers, 200 layers are far from the end, and in the past two years, some giants have begun to target 1000 layers of stacked 3D NAND.

It's important to note that 1000-layer NAND isn't that easy to do. Theoretically, stacking more than 1000 layers of NAND is possible, but deposition and etching during the stacking process need to be addressed.

Specifically, in the development process of 2D NAND, lithography technology is the key process to promote its development, 3D NAND is completely different, where memory cells are vertically stacked to increase capacity.

Lam According to Bart van Schravendijk, CTO of Research Dielectrics, 3D When the NAND is stacked to 96 layers, the actual number of layers deposited has reached more than 192 layers, and the uniformity of the silicon nitride layer will become a key parameter affecting the performance of the device.

In addition to that, 3D The most difficult part of the NAND process is the etching process that requires a high aspect ratio. In a 3D NAND structure, a tiny circular channel must be etched from the top layer to the bottom layer of the device through an etching process to connect the memory cells vertically.

Lam For 96-layer 3D NAND wafers, the etching aspect ratio is as high as 70:1, and each wafer has a trillion of these tiny holes, which must be parallel to each other, according to Research. As the number of stacks increases, so does the difficulty of the etching process.

This also means that if the number of layers stacked exceeds 1,000 in the future, chip manufacturers may need to face increasingly complex and expensive processes. At that time, the storage industry needs to find new solutions to continue to meet people's growing storage needs, of course, this may also be a new storage medium, the major manufacturers are also well aware of this, and are currently actively investing in research and development, such as: FeRAM, MRAM, PCM, RRAM, etc., however, which device can stand out and become the next generation of non-volatile memory devices, it will take time to give an answer.

In the NAND market, a fierce battle has begun

Samsung's 1000-layer NAND plan

Samsung Electronics is actively exploring "hafnium ferroelectric" as a next-generation NAND flash memory material, and hopes that this new material can be stacked with more than 1,000 layers of 3D NAND and implement petabyte-level SSDs.

Hafnium ferroelectric oxide materials are expected to replace oxide films currently used in 3D NAND stacking technology, thereby improving the durability and stability of chips. Samsung executives predict that by around 2030, its 3D NAND could be stacked with more than 1,000 layers.

According to South Korean media, citing industry insiders, Samsung is working with the Korea Advanced Institute of Science and Technology (KAIST) to step up the development of 3D NAND technology based on hafnium ferroelectrics dioxide. The results of their research and development will be held at IEEE 2024 in Hawaii, USA Exhibited at the VLSI Technology & Circuits Symposium.

SK hynix develops a next-generation NAND flash memory solution for mobile devices

In May of this year, SK hynix announced that it has developed ZUFS (Zoned), a mobile NAND flash solution for on-device AI UFS）4.0。

SK hynix said: ZUFS 4.0 is a next-generation mobile NAND flash solution that delivers the industry's highest performance and is optimized for on-device AI phones.

ZOFS manages the data generated by smartphone applications according to the characteristics of each data. Unlike the existing UFS hybrid storage method that does not divide into regions, ZOFS can zone and store data for different purposes and frequency to improve the running speed of the mobile phone operating system and the data management efficiency of storage devices.

As a result, ZUFS will improve the runtime of the mobile app by approximately 45% compared to the existing UFS in the long-term environment. In addition, ZUFS has achieved a more than 4-fold improvement in storage read and write performance, resulting in a 40% increase in product lifespan.

SK hynix provided customers with initial trial products, and based on these product specifications, we collaborated with customers to develop JEDEC-compliant 4.0 products. The company will start mass production of ZUFS 4.0 products in the third quarter of this year.

Micron announces 232-layer QLC NAND is in production now

In April of this year, Micron announced its 232-layer QLC NAND is in production now and is shipping in select Crucial solid-state drives (SSDs). At the same time, Micron's 2500 NVMe SSD has also been mass-produced for enterprise storage customers and sampled to PC OEMs.

Micron 232-layer QLC NAND delivers unmatched performance for mobile devices, client devices, edge, and data center storage, with key benefits including: industry-leading storage density of up to 28% higher than the competition's latest offerings; Industry-leading 2400 MT/s1 NAND input/output (I/O) speeds, up to 50% faster than the previous generation; 24% better read performance than the previous generation; Programming performance is up to 31% better than the previous generation.

At this moment, the NAND flash memory situation is very good

Since the fourth quarter of 2023, the environment of the storage industry has improved significantly, the downstream market demand has recovered, and the sales volume of storage products has also achieved significant year-on-year growth.

According to TrendForce's latest research report, high-capacity SSD orders began to emerge due to the expanded adoption of enterprise SSDs for AI servers since February, and the continuous increase in inventory reserves of PC and smartphone customers due to rising prices, driving the volume and price of NAND Flash in the first quarter of 2024, with revenue increasing by 28.1% quarter-on-quarter to US$14.71 billion.

The biggest change in the ranking this quarter was when Micron overtook Western Digital to take fourth place. This is mainly due to Micron's price and shipment volume in the fourth quarter of 2023, which is slightly lower than other competitors, so the revenue growth rate in the first quarter was 51.2%, reaching US$1.72 billion.

Looking at the trend in the second quarter, the NAND Flash inventory level of PC and smartphone customers has been high, and the growth of consumer terminal orders this year has not been better than expected, and brand buyers have become more conservative in stocking. At the same time, the average price of NAND Flash products continued to rise by 15% in the second quarter, driven by the doubling of orders for high-capacity enterprise SSDs, and it is estimated that NAND Flash revenue in the second quarter will increase by nearly 10% quarter-on-quarter.