Engineers at IBM Research in Zurich, Switzerland claim they've come up with a breakthrough in phase change memory (PCM) technology that, for the first time, would allow it to store data for longer periods, potentially paving the way for lower cost solid state chips that are faster and more reliable than today's multi-level cell (MLC) flash memory chips. The trick is in figuring out a solution to a problem called "drift."
PCM is nonvolatile memory technology that stores data in small cells of chalcogenide, a compound used in rewritable optical discs. Chalcogenide changes physical states between crystalline and amorphous when heat is applied, and because it's nonvolatile, it doesn't cough up your data when you flip the power switch like RAM does. The problem with PCM is that the cells randomly drift over time, leading to data corruption.
IBM has figured out a way to sidestep the issue of drift and created PCM chips that can store two bits of data per cell in a 200 k-cell array implemented in a 90nm process technology. By applying an advanced coding technique -- the geeky details of which you can read here -- IBM is able to correct for drift-related errors.
"We apply a voltage pulse based on the deviation from the desired level and then measure the resistance. If the desired level of resistance is not achieved, we apply another voltage pulse and measure again – until we achieve the exact level," said Haris Pozidis, manager of memory and probe technologies at IBM Research Zurich.
In a worst case write latency scenario of about 10 microseconds, IBM says the technology still represents a 100x performance increase over even the most advanced flash memory on the market today.
Image Credit: IBM