Macronix, one of the world’s largest producers of flash memory, has produced a new kind of flash memory that can survive more than 100 million program/erase (PE) cycles — most likely long enough to persist until the end of human civilization. By comparison, the NAND cells found in conventional flash memory — as in commercial SSDs — generally have a lifespan of just a few thousand PE cycles.
For such a huge advance you would expect an equally vast technological leap — but in this instance, that’s certainly not the case. Macronix just adds a bit of heat — literally, each of Macronix’s new memory cells contains a heating element that can deliver a jolt of 800C (1472F) heat to the cell, healing it and preventing wear-out. Furthermore, 100 million PE cycles is a low-ball estimate: In reality, Macronix’s new flash might survive billions of cycles — but it would take so long to test that the company doesn’t yet know.
Why does heat fix a flash memory cell? It’s all down to the physical structure. NAND flash is constructed from floating-gate transistors, which are exactly what they sound like. Basically, the control gate (which controls the flow of electricity across the transistor) floats above an additional oxide layer. In effect, the bit value of the cell is stored in this floating gate. To trigger the gate — to change the bit value — a certain threshold of current is required to jump through the oxide layer. Over time, this oxide layer degrades, eventually causing the cell to fail.
By applying heat, this oxide layer can be annealed, returning it to its base state. Macronix has known about this annealing effect for years — but historically its testing involved putting a bunch of memory chips in an oven and baking at 250C (482F) for a few hours. Obviously this wasn’t the best solution for consumer electronics, and so a new method had to be devised. Ta’da: Macronix’s NAND memory cell with built-in heat plates.
Macronix intends to capitalize on the self-healing flash breakthrough, but he would not give details about how and when. He was more forthcoming about when the flash industry should have worked in this technology. “It took a leap of imagination to jump into a completely different regime…very high temperature and in a very short time,” says Lue. “Afterward, we realized that there was no new physics principle invented here, and we could have done this 10 years ago.”