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Ferroelectric Storage Technology Makes New Progress.

According to reports, Chinese scientists have successfully developed a fatigue-free ferroelectric material and published their research findings in the international top academic journal "Science."

Traditional storage chips have been limited by the number of read-write cycles of ferroelectric materials, and their stability decreases over time, which has long constrained the further development and application of storage chips.

The Chinese research team, based on the two-dimensional sliding ferroelectric mechanism, has developed a new type of two-dimensional layered sliding ferroelectric material (3R-MoS2). The storage chips made from this material are expected to break through the read-write cycle limitation and achieve unlimited read-write cycles.

The core of this research lies in using "interlayer sliding" to replace the "ion movement" of traditional ferroelectric materials. Through AI-assisted cross-scale atomic simulation analysis, the micro-physical mechanism of the fatigue resistance of two-dimensional sliding ferroelectric materials has been revealed.The figure below shows the fatigue resistance analysis of 3R-MoS2 ferroelectric devices.

Experiments have shown that the ferroelectric chip devices made from this material still show no decay in electrical polarization after undergoing 4 million cycles of reversed polarization in the electric field. This technology not only greatly improves the reliability and durability of storage chips but also helps to reduce costs and increase storage density. It is expected to play an important role in extreme environment applications such as aerospace and deep-sea exploration, as well as in wearable devices and flexible electronic technology in the future.

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The value of ferroelectric memory

Ferroelectric memory is a type of random access memory that combines the fast read and write capabilities and data retention of DRAM with the characteristics of other stable storage devices. It is not as dense as DRAM and SRAM, but it has fast storage speed under low power consumption.

Although it may not replace these technologies, it has a wide range of application prospects in small devices, such as PDAs, mobile phones, power meters, smart cards, and security systems. The development of ferroelectric memory began in 1921, and in 1993, Ramtron International Corporation in the United States successfully launched the first 4K-bit FRAM product. Its technical features are different from floating gate memory, using artificially synthesized lead zirconate titanate material, and storing data by forming polarization charges through the reversal of ferroelectric domains under an electric field, with advantages such as non-volatility, no write delay, fast write speed, and unlimited write life. Its principle is to use the ferroelectric effect of ferroelectric crystals to achieve data storage, with characteristics of non-volatility and anti-magnetic field interference.

Ferroelectric storage technology was proposed as early as 1921, and it was not until 1993 that Ramtron International Corporation in the United States successfully developed the first 4K-bit ferroelectric memory FRAM product. All FRAM products are manufactured or licensed by Ramtron Corporation. FRAM has new developments, using a 0.35um process, launching 3V products, and developing "single-tube single-capacitor" storage unit FRAM, with a maximum density of up to 256K bits.FRAM leverages the ferroelectric effect of ferroelectric crystals for data storage. The ferroelectric effect refers to the movement of the central atoms of the crystal under the influence of an applied electric field, reaching a stable state; when the electric field is removed from the crystal, the central atoms remain in their original positions. This is because the middle layer of the crystal is a high-energy state, and the central atoms cannot cross the high-energy state to reach another stable position without obtaining external energy. Therefore, FRAM retains data without the need for voltage, and does not require periodic refreshment like DRAM. Since the ferroelectric effect is an inherent polarization characteristic of ferroelectric crystals, it is unrelated to electromagnetic effects, so the content of FRAM memory is not affected by external conditions such as magnetic fields, and can be used like ordinary ROM memory, with non-volatile storage characteristics.

The characteristics of FRAM are fast speed, capable of operating like RAM, extremely low read and write power consumption, and there is no issue of maximum write times like E2PROM. However, constrained by the characteristics of ferroelectric crystals, FRAM still has a limit on the maximum number of accesses (reads).

FRAM products have the advantages of both RAM and ROM, with fast read and write speeds and can be used like non-volatile memory. Due to the inherent shortcomings of ferroelectric crystals, the number of accesses is limited, and beyond the limit, FRAM no longer has non-volatility. However, it does not mean that FRAM will be scrapped after exceeding the limit, but it simply loses its non-volatility and can still be used like ordinary RAM.

FRAM vs. E2PROM: FRAM can be an alternative to E2PROM, and it has a much faster access speed in addition to the performance of E2PROM. However, before deciding to use FRAM, it must be determined that there will be no danger in the system once the 1 million access limit for FRAM is exceeded.

FRAM vs. SRAM: In terms of speed, price, and ease of use, SRAM is superior to FRAM. However, from the overall design perspective, FRAM still has certain advantages. For example, if the design requires about 3K bytes of SRAM and a few hundred bytes for the E2PROM configuration to save the boot code, non-volatile FRAM can save the boot program and configuration information. If the maximum access speed of all memories in the application is 70ns, a single FRAM can be used to complete this system, making the system structure more simple.

FRAM vs. DRAM: DRAM is suitable for occasions where density and price are more important than speed. For example, DRAM is the best choice for graphics display memory, where a large number of pixels need to be stored, and recovery time is not very important. If there is no need to save the previous content when starting up next time, using volatile DRAM memory is sufficient. The role and cost of DRAM are incomparable to FRAM, and it has been proven that DRAM cannot be replaced by FRAM.

FRAM vs. Flash: The most commonly used program memory is Flash, which is very convenient and increasingly cheaper. The program memory must be non-volatile and relatively low-cost, and it should be relatively easy to rewrite. However, using FRAM is limited by the number of accesses, and it will lose its non-volatility after multiple reads.