Taiwanese engineers defeat limitations of flash memory

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Here’s something you might not know about the memory in the USB flash drives you use every day to transfer files and programs from computer to computer—the number of times you can write and erase files and programs to the flash drive has a limit before it becomes unusable. “Flash wears out after being programmed and erased about 10,000 times,” said an article in the magazine IEEE Spectrum, although some drives are capable of reaching 100,000 and even 1 million write-erase cycles. The write-erase cycles degrade insulation and essentially make your USB flash drives into paperweights.

Taiwanese engineering firm Macronix has proposed a “self-healing” NAND flash memory solution that can survive over 100 million cycles of writing and erasing files and programs, so you probably won’t have to worry about ever needing to find a new flash drive, ever. The workaround that the firm found was heat, although they admitted it was impractical at the moment despite its ability to heal damaged sectors. “The long baking time is impractical for real time operation,” they said, further stating they would need to heat the entire memory chip for a few hours at 250 degrees Celsius.

They redesigned a flash memory chip to include onboard heaters to anneal, or alter the properties of a metal via heat treatment, small groups of memory cells. Applying a brief jolt of heat to a very restricted area within the chip at 800 degrees Celsius returns the cell to a useable, or “good” state. “The annealing can be done infrequently and on one sector at a time while the device is inactive but still connected to the power source. It would not drain a cellphone battery,” said project member Hang‑Ting Lue.

Macronix estimates that the flash memory cells could beat the 10,000 cycle limit by lasting for as much as for 100 million cycles but a commercial product is not imminent. Instead, Macronix will present their approach—very high temperature in a very short time— this month at the IEEE International Electron Devices Meeting (IEDM) from December 10 to 12 in San Francisco. This is the forum for presenting breakthroughs in semiconductor and electronic device technology.