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06.01.2024 14:23, Gennady Detinich
As became known source, at the IEDM 2023 conference held in December, Micron announced behind closed doors the development and use of a huge-capacity FeRAM memory crystal. FeRAM memory has been produced for about 20 years, but these are traditionally low-capacity chips from 8 to 128 Mbit. Micron’s development against this background is amazing with a 32 Gbit die capacity, which can be compared to the rise of new non-volatile memory.
A fragment of a Micron document from the presentation of dual-layer FeRAM memory. Image source:
FeRAM memory is faster than NAND memory. In this indicator, it is close to DRAM RAM. At the same time, FeRAM chips retain charge in the cells even without power supply to them, like other non-volatile memory. Also, FeRAM memory is more resistant to wear, which again makes it preferable for use in data storage devices. Finally, FeRAM is not afraid of radiation, magnetic fields and temperature fluctuations, which predetermined its fate in machine tools, instruments and on-board equipment in the aerospace industry.
Despite a wide range of advantages, FeRAM memory has not become a mass phenomenon. Its cell density is very, very low, and mass NAND memory with its colossal capacity crystals did not give FeRAM any chance to penetrate into the data storage area. However, even the 3D XPoint memory (Intel Optane trademark), which Micron developed together with Intel, failed to do this. The availability and low cost of NAND played a negative role in the sad fate of this seemingly promising non-volatile memory.
It’s not hard to imagine that Micron’s informal announcement of the 32 Gbit FeRAM chip could be considered a significant event. The Blocks & Files website provides a fragment of an image of a document from the presentation of a memory chip, which is not available for public viewing.
High-capacity FeRAM chips will boost the development of generative artificial intelligence models, Micron says. They work faster than NAND and have tremendous wear resistance. An experienced Micron chip can withstand up to 1015 rewrite cycles. This is several orders of magnitude higher than competing FeRAM chips from Fujitsu, Infineon, SK Hynix and Toshiba, not to mention a measly thousands of cycles if we’re talking NAND chip wear resistance. By the way, the company calls the new memory NVDRAM (non-volatile dynamic random access memory). Obviously, she did not dare to call it NVRAM, so that her FeRAM would not be confused with other types of non-volatile memory.
The company’s stated write speed for FeRAM chips is 70-120 ns, while NAND write cycles are closer to 300 µs. The data retention time in FeRAM memory (charge in the cell) reaches 10 years.
It can be assumed that Micron gained access to FeRAM patents and technologies after acquiring the assets of the Japanese company Elpida in 2013. Elpida itself did not develop this type of memory, but the Taiwanese Inotera Memories and Nanya Technology factories that it owned at that time were previously owned by Infineon and produced FeRAM memory chips.
The FeRAM switching element is typically made of lead zirconate titanate (PZT) piezoceramic. This material retains polarization even after removing the external control signal – the electromagnetic field. Roughly, we can say that each FeRAM cell consists of a control transistor and a piezoceramic capacitor. It is the inclusion of the piezoceramic element that makes the cell very large. How Micron solved this problem is not reported.
