Startup Showcases 7 bits-per-cell Flash Storage with 10 Year Retention
takyon writes:
Startup Showcases 7 bits-per-cell Flash Storage with 10 Year Retention
Floadia Corp., a Series C startup from Japan, issued a press release this week to state that it has developed storage technology capable of seven bits-per-cell (7bpc). Still in the prototype stage, this 7bpc flash chip, likely in a WORM [(Write Once Read Many)] scenario, has an effective 10-year retention time for the data at 150C. The company says that a standard modern memory cell with this level of control would only be able to [retain] the data for around 100 seconds, and so the secret in the design is to do with a new type of flash cell they have developed.
The SONOS cell uses a distributed charge trap design relying on a Silicon-Oxide-Nitride-Oxide-Silicon layout, and the company points to an effective silicon nitride film in the middle where the charges are trapped to allow for high retention. In simple voltage program and erase cycles, the company showcases 100k+ cycles with a very low voltage drift. The oxide-nitride-oxide layers rely on SiO2 and Si3N4, the latter of which is claimed to be easy to manufacture. This allows a non-volatile SONOS cell to be used in NV-SRAM or embedded designs, such as microcontrollers.
It's actually that last point which means we're a long time from seeing this in modern NAND flash. Floadia is currently partnering with companies like Toshiba to implement the SONOS cell in a variety of microcontrollers, rather than large NAND flash deployments, at the 40nm process node as embedded flash IP with compute-in-memory properties. Those aren't at 7 bits-per-cell yet, to the effect that the company is promoting that two cells can store up to 8-bits of network weights for machine learning inference - when we get to 8 bits-per-cell, then it might be more applicable. The 10-year retention of the cell data is where it gets interesting, as embedded platforms will use algorithms with fixed weights over the lifetime of the product, except for the rare update perhaps. Even with increased longevity, Floadia doesn't go into detail regarding cyclability at 7bpc at this time.
Related: Is Octa-Level Cell (OLC) NAND Possible? We May Find Out This Year
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