A Breakthrough for the "1000-Layer Era" in Flash Memory: What are Kioxia and Sandisk's MSA-CBA?

*This article is a deeper explanation that organizes the technical background and industry intentions based on the content of the short video above.

What is happening

Kioxia and Sandisk have unveiled a technology called "MSA-CBA" as a next-generation structure for 3D flash memory.

MSA-CBA is a structure that stacks multiple memory cell arrays and combines them with CMOS, which is the control circuit. Simply put, it is a technology that aims for higher-density NAND flash by precisely bonding separately manufactured structures together, rather than just stacking them endlessly on a single wafer.

The notable point this time is that QLC operation was demonstrated with this structure. QLC is a method of recording 4 bits of information in a single memory cell. While it makes it easier to increase capacity, it requires fine differentiation of voltage levels, making control more difficult.

What is this technology?

Current NAND flash is dominated by "3D NAND," which stacks memory cells vertically. NAND flash is a non-volatile memory used in smartphones and SSDs. Non-volatile means that data remains even when the power is turned off.

3D NAND has increased capacity by stacking cells vertically, much like making a building taller. However, as the number of layers increases, the problems also grow. Cell current becomes weaker, making read/write stability more difficult. Furthermore, the wafer becomes prone to warping during manufacturing, which affects yield. Yield refers to the percentage of manufactured chips that can be used as good products.

MSA-CBA can be seen as a technology that "changes the way of stacking" in response to this limitation. Rather than simply increasing the number of layers, it aims to create a path toward exceeding 1000 word lines in the future by stacking multiple cell arrays. A word line is a wiring used to select memory cells and is an important indicator when considering the number of layers in 3D NAND.

Why is it important now?

The background to the attention this technology is receiving is the increase in data volume in the AI era.

With the spread of generative AI, the data that needs to be stored, such as training data, inference logs, images, and videos, continues to increase. When people think of AI, GPUs and HBM tend to get the attention, but storage that saves large amounts of data is also indispensable. Increasing the density of NAND flash used in SSDs is one of the foundational technologies supporting AI infrastructure.

On the other hand, it is becoming difficult for NAND flash to evolve solely through the extension of existing methods. There are limits to miniaturization, and increasing the height of 3D NAND also hits walls related to current, stress, and manufacturing costs. This is where structural innovations like MSA-CBA become important.

It is thought that future NAND competition will shift not just from "how many layers can be stacked," but to "how to manufacture separately, how to bond, and how to mass-produce stably."

Summary

Kioxia and Sandisk's MSA-CBA is an important structural technology for increasing the height of 3D NAND.

The point is not simply to increase the number of layers. It lies in the fact that it demonstrated QLC operation with a structure that stacks multiple cell arrays, showing the potential for future 3D flash with over 1000 word lines.

However, research demonstration and mass production are different things. From here on, the focus will be on how far bonding precision, yield, reliability, and cost can be raised to mass-production levels.

▼ In the **paid magazine "NEOTechWorld Deep Dive"**, the following is organized:https://note.com/neo_tech_world/n/n3edb09aa6542

• Detailed mechanism of the MSA-CBA structure and technical differences from conventional methods

• Trends and technical gaps among competitors such as Samsung, Micron, and YMTC

• Challenges for mass production (yield, cost, and QLC reliability)

• The positioning of flash memory in the AI data center market

• Conditions for Kioxia to win and risk scenarios

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References and Citations

• 2026 IEEE/JSAP Symposium on VLSI Technology and Circuits Technical Highlights

• KIOXIA "3D Flash Memory “BiCS FLASH™”"

• Sandisk "Kioxia and Sandisk Unveil Next-Generation 3D Flash Memory Technology"

• Mynavi News "Notable Papers in the Semiconductor Memory Field"