Ziguang’s Changjiang storage has taken an important step in domestic flash memory, and has begun mass production of 64 layer stack 3D flash memory. Based on the xstacking technology developed by Changjiang storage, the core capacity is 256gb.

In addition to the mass production of 64 layer 3D flash memory, Changjiang storage also announced another important news today, that is, xstacking 2.0 stack technology, which will be on the third generation 3D flash memory of Changjiang storage (the first generation is 32 layers, small production, and the current mass production of 64 layers is the second generation). The relevant technology will be announced at the upcoming IC China 2019 conference.

With the increase of the stack layers of 3D flash memory, a major challenge is that the peripheral IO circuits continue to grow and occupy the capacity of the flash memory core. Usually, the IO peripheral circuits account for 20-30% of the area. With the increase of the stack layers to 128 layers or higher, the proportion of peripheral circuits may be as high as 50%. Therefore, reducing the area of these circuits has become an important test of 3D flash memory.

Xstacking technology of Changjiang storage is a stack technology developed on the CIS sensor chip of Wuhan Xinxin technology. It places the peripheral circuit on the storage unit. The peripheral circuit and the storage unit are two wafers, and the size of the two bare chips is the same, which means that its CMOS usable area is much larger than that of other traditional 3D NAND architectures, so as to achieve higher storage density.

It not only improves the capacity utilization, but also provides unlimited possibility for introducing the innovative function of NAND peripheral circuit to realize the customization of NAND flash memory in addition to the control circuit.

According to Ziguang’s information, xtacking can process peripheral circuits and memory cells on two independent wafers, which is conducive to selecting more advanced manufacturing processes. When the two wafers are completed, the innovative xtacking technology can bond the two wafers through billions of vertical interconnection channels (via) in only one processing step.

At present, the target value of the world’s fastest 3D NAND I / O speed is 1.4gbps, while most NAND suppliers can only supply speeds of 1.0 Gbps or lower. Using xtacking technology, we are expected to significantly increase the NAND I / O speed to 3.0gbps, which is equivalent to the I / O speed of DRAM DDR4.

According to official news, 64 layer flash memory based on xstacking stack technology is mainly used for solid state drives, UFS and other products to meet the needs of data centers, enterprise servers, personal computers and mobile device manufacturers. The third generation flash memory based on xstacking 2.0 technology is widely used in data centers, enterprise servers, personal computers and mobile devices, and will open a new chapter of high-performance and customized NAND solutions, with a higher overall positioning.

Due to the lack of disclosure of detailed information, it is still uncertain how many layers the third-generation flash memory of xstacking 2.0 technology is. However, according to the previous disclosure, Changjiang storage plans to shorten the technology gap with Samsung, Toshiba and other companies in 2020, so it will skip 96 layers and directly enter 128 layers of stack flash memory, so that it can approach the international advanced level in mass production next year.

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