Researchers at International Business Machines, commonly referred to as IBM, have recently announced a significant breakthrough in phase-change memory. Scientists and researchers have spent several years searching for a non-volatile memory standard which is faster than NAND flash that simultaneously provides superior power characteristics, better longevity, as well as higher densities.
Phase change memory has been in development and seems to be one of the more promising technologies. IBM researchers have declared that they have discovered an innovative way to store up to three bits of data per “cell” of memory. Past work in the field has been limited to a single bit of data per memory cell.
“Phase change memory exploits the properties of a metal alloy known as chalcogenide. Applying heat to the alloy changes it from an amorphous mass into a crystal lattice with significantly different properties,”
said Joel Hruska from Extreme Tech. Scientists have long known that chalcogenide could exist in states between crystal lattice or amorphous, but building a solution that could exploit these in-between states to store more memory has been extremely difficult. While phase-change memory works on very different principles than NAND flash, some of the problems with scaling NAND density are conceptually similar to those faced by PCM.
“Storing multiple bits of data in NAND flash is difficult because the gap between the voltage levels required to read each specific bit is smaller the more bits you store. This is also why TLC NAND flash, which stores three bits of data per cell, is slower and less durable than MLC (2-bit) or SLC (single bit) NAND,” Hruska added.
Researchers at IBM have found new ways of storing three bits of data in a 64K array for one million endurance cycles as well as at elevated temperatures.
“Phase change memory is the first instantiation of a universal memory with properties of both DRAM and flash, thus answering one of the grand challenges of our industry,” said a researcher from IBM, Dr. Haris Pozidis. Dr. Pozidis is the manager of non-volatile memory research for IBM Research. “Reaching 3 bits per cell is a significant milestone because at this density the cost of PCM will be significantly less than DRAM and closer to flash.”