Is your new flash memory device really new? Can you determine if it’s a recycled chip? University of Alabama engineers can.
Their simple method is based on the relatively high voltages — about 20 volts — needed to program and erase flash. The more a cell is programmed and erased, the more defects will accumulate in the oxide. This leads to an increase in the amount of current that leaks through the transistor when it’s supposed to be off, and it also slows down the rate at which charge moves through the device. The result is a slowdown in the memory’s erase time as an indicator of a chip’s age.
The erase-time technique, which could allow an app on a smartphone to examine its own storage for recycled parts, was demonstrated to identify recycled flash with as little as three percent usage with 100 percent confidence.