Effect of Selenium Doping on GeSb for Phase Change Memory Applications

Phase change memory(PCM) has been focused as the alternative for next generation memory since it shows several advantages such as low fabrication cost, a scalability below 20nm design rule, large endurance cycles, and compatibility with semiconductor process. However, there still exist essential problems that are mainly determined by the properties of a phase change material. For example, the PCM cells composed of GeSbTe alloy relatively show low crystallization temperature, slow operation speed, and narrow resistance margin between reset and set state in respect of commercialization of PCM.

In our study, the GeSb film was selected as phase change material due to its fast crystallization speed and selenium was employed doping element for increasing thermal stability and the margin between high and low resistance. When the selenium was incorporated into GeSb film up to 8 at %, the crystallization temperature increased from 150^oC to 225^oC and the amorphous sheet resistance was elevated more than 13 times compared with undoped GeSb film. In addition, the resistance margin of the film significantly increased more 2 order of magnitude than that of GeSbTe film. The phase separation was found in the GeSb film doped with selenium over 8 at % and this was proved by XRD and XPS analyses. As a consequence, Selenium doped GeSb film was strongly demonstrated as phase change material of PCM cell due to its thermal stability and large resistance margin including high crystallization speed.