RESET Distribution Improvement of Phase Change Memory: The Impact of Pre-Programming

Some nonvolatile phase change memory (PCM) cells with 80-nm heating electrodes are found very difficult to RESET at 3 mA, which directly affects the RESET distribution of the PCM. The large crystal grains with hexagonal structure in the active phase change area, discovered by transmission electron microscope, are the major reason. One preprogramming testing method is introduced, and the resistance distributions of the PCM cells before and after preprogramming are presented. Results show that the large hexagonal crystal grains have been eliminated, thus the resistance distributions have been greatly improved after preprogramming.