Let me talk about a fact first, that is, Yangtze Memory in mainland China has become the world's first manufacturer to mass-produce 232-layer 3D NAND flash memory chips. Its technology has surpassed Samsung , Micron , SK Hynix , Kioxia and other giants.
In fact, Yangtze Memory has kept a low profile and has not announced this fact, but TechInsights found that SSDs using Yangtze memory chip particles were too powerful, so they disassembled this Hikvision CC700 2TB solid state drive , and finally discovered that this SSD uses a 232-layer 3D NAND structure.
As a result, the news flooded the Internet, and netizens were very excited because this may be the first time that a Chinese mainland manufacturer ranks first in the world in terms of technology in the field of semiconductors.
Then the question arises. How can a company that has been established for only more than 7 years surpass technological giants such as Samsung and Micron? Here I would like to mention a 3D technology developed by Yangtze Memory, which is Xtacking, also known as "crystal stack".
We know that the common way to improve the performance of chip is to upgrade the process, such as from 14nm to 10nm, then 7nm, 5nm, and 3nm. This method is planar shrinkage.
In memory chips such as NAND, it has been found that when the process is improved to about 15nm and then shrunk, the data will be unstable and may be lost or confused.
NAND is used for storage devices such as SSD. Once there is a problem with the stored data, no matter how high the performance of the device is, no one will use it. Data stability and security are above all else.
So memory chip manufacturers, after 15nm, no longer improve the process, but change their strategy. They no longer shrink the transistor from the plane, but use upper and lower stacking to become a 3D structure.
The XX layer 3D NAND flash memory means that this chip uses the stacking technology of upper and lower XX layers. The more stacked, the more advanced the technology and the higher the storage density.
The memory chip is actually divided into two functional areas. One is the unit responsible for storing data, and the other is the unit for reading/storing data. These two blocks are independent of each other but closely related.
Yangtze Memory has found in continuous research that if the unit that reads/stores data can be scaled down, such as upgrading to 14nm, 12nm, etc., compared with the 15nm process, the speed of reading/storing data can be greatly improved.
As for the unit that stores data, the process cannot be upgraded and can only be maintained at 15nm or more mature process. Once the process is upgraded, the stability will decrease.
So Yangtze Memory had a bold idea. Since the two parts are independent of each other and have different characteristics, they might as well separate them and use different processes to manufacture them.
Yangtze Memory's Xtacking was born in this way. It is a 3D three-dimensional structure in which the storage unit and the unit that reads/stores data belong to different wafers. The unit that stores data like
is manufactured using a more mature process to ensure the stability of the data. However, the unit that reads/stores data is manufactured using a more advanced process to ensure the speed of reading/writing, and the two are connected through circuits.
In this way, the 3D NAND flash memory manufactured can not only ensure the stability of data, but also ensure good read/write performance, achieving the purpose of balancing both.
also uses Xtacking technology to manufacture chips, which can also greatly shorten the chip cycle, because the read/write part and the storage part can be manufactured separately, using different processes, which can greatly improve production efficiency. Therefore, Yangtze Memory relied on Xtacking technology to surpass giants such as Samsung and Micron, and became the first in the world to mass produce 232-layer 3D NAND.
Of course, the technology has surpassed it, but the consequences are serious. The United States was frightened and added Yangtze Storage to the "entity list" and imposed restrictions on some advanced equipment. It can be predicted that under such circumstances, it will be more difficult to expand production of this advanced technology. It is estimated that the window period for seizing the market through technology will be missed, and this is also the purpose of the United States.
