Heating NAND brings it back to life

Read an article today in ARS Technica titled NAND flash gets baked, lives longer that researchers at Macronix have come up with a technique that rejuvenates NAND bit cells by heating them.  The process releases the bit cells captive electrons and returns it back to a fresh NAND cell.

As discussed previously in this blog (e.g., see The End of NAND is near, maybe… and What eMLC and eSLC do for SSD longevity) as NAND technology shrinks to smaller transistor diameters, their longevity and durability decreases proportionally. Which means that with denser NAND chips coming out over the coming years, they will become increasingly short lived.

With this new approach and an awful lot of engineering to zap a NAND bit cell with intense heat (800C) can take dead NAND cells and bring them back to life. Apparently this rejuvenation process has been known for some time and had been in use for phase change memory but had not been applied to NAND cells in memory.  They were heating batches of NAND cells for hours at 200C but this wouldn’t be very practical in production.

The new NAND memory cells are designed with a resistive heating element on top of them, which when enabled can heat the NAND bit cells beneath them. According to some news reports I’ve read this enables the NAND cell to go from 10K P/E cycles to 100K P/E cycles.  And the heat only needs to be applied in occasional pulses to keep cells operating within parameters.   As such, it can be used sparingly and not cost too much energy in the process.

Another side effect of heating is that erase cycles operate faster than at normal temperatures, which now adds the possibility of heat assisted NAND cells.   Erasure being one of the key bottlenecks to NAND write performance anything that can speed this up would help.

Hot NAND may have some life in them after all.



Image: Blow Torch by xlibber