Macronix Cooks Up Indestructible NAND Flash Memory Chips


We don’t normally think of heat as being a desirable quality when it comes to consumer electronics. When your chips are running at high temperatures all the time, their life span can be reduced quite dramatically, whilst performance can be killed due to “throttling”, and in extreme cases, your hardware could even burn itself out completely, for example if an older laptop is left lying on the bed for too long.

But all this goes out the window when it comes to flash memory chips, where researchers have found that extreme temperatures exceeding 800 Celsius can make them practically indestructible.

According to the Taiwanese memory manufacturer Macronix, ‘baking’ flash memory chips in such extreme heat has the seemingly unlikely effect of extending a typical NAND cell’s lifetime so that it can survive as many as 100 million write cycles without any loss of performance.

Spectrum IEEE goes into more extensive detail about how this works, but to put things into perspective, the average multi-level cell (MLC) and triple-level cell (TLC) NANDs that drive most flash drives today last for around 10,000 and 1,000 write cycles respectively, varying only slightly by manufacturer.

So the ability to get 100 million cycles out of a flash memory drive is a pretty big deal by any stretch of the imaginations – effectively, we’ll never need to replace a flash drive ever again.

Previously, the problem with flash memory is that each time we write new information on a NAND chip, the insulation surrounding its transistors is ever so slightly eroded. After a while, it reaches the point where it becomes impossible to write any more data onto the chip.

But Macronix says that it’s actually possible to “heal” the chips, by exposing them to temperatures just above 800C for a few milliseconds. Doing so isn’t as easy as it sounds of course – we can’t just stick our chips in the oven like we do at home! But what we can do – or rather, what Macronix did, is to built specialized hardware into the chips that can deliver short but extreme bursts of heat as and when the chip needs a ‘pick me up’.

Macronix took its idea from technology used with phase-change RAM (or PCRAM), which is one of the main alternatives to NAND. In PCRAM, the bits are stored in a material called chalcogenide glass, which can be either conductive or insulating. Heating this glass changes its physical state, allowing each bit to be marked as empty or written.

Macronix, who says it intends to “capitalize on its findings”, will present the results of its findings later this month at the International Electron Devices Meeting 2012. It’ll be interesting to see what they have planned, given the obvious risks of such a technology.

Whilst Macronix says that the heating process doesn’t need to be done all that often, the big question is how will it do so? Building such hardware into the chips seems the easiest option, but could this present a fire hazard?

But if Macronix can come up with a commercially viable product, we could well see SSDs take over and become the storage medium of choice, at least until memresistors take over.