Phase separation behavior of Ge₂ Sb₂ Te₅ line structure during electrical stress biasing

We report the breakdown behavior of a patterned Ge2 Sb2 Te5 multiline structure during the voltage-driven electric stress biasing. Scanning Auger microscope analysis shows that the breakdown process accompanies with a phase separation of Ge2 Sb2 Te5 into an Sb, Te-rich phase and a Ge-rich phase. The phase separation is explained by the incongruent melting of Ge2 Sb2 Te5 based on the pseudobinary phase diagram between Sb2 Te3 and GeTe. It is claimed that this phase separation behavior by incongruent melting provides one of the plausible mechanisms of the device failure in a phase change memory.