TEM observation of void formation and migration in phase change memory devices with confined nanoscale GeSbTe.

The reliability of Ge-Sb-Te phase-change memory (PCM) devices has been limited by failure due to void formation and this still remains one of the critical issues affecting their use in storage-class memory applications. To directly observe the void formation processes in real-time, we implemented switching of PCM devices by applying set and reset voltage pulses to a GeSbTe (GST) cell inside a transmission electron microscope (TEM). The TEM observations directly show that a void nucleates preferentially near the TiN bottom electrode in the GST cell, where the temperature is the highest.