Spectromicroscopic investigation of lateral-type Ge₂Sb ₂Te₅ device failure

Scanning photoelectron microscopy with synchrotron radiation was used to investigate the failure phenomena of phase-change memory devices based on the Ge₂Sb₂Te₅ (GST) system with a native oxygen impurity. The scanning photoelectron microscopy (SPEM) images and spectra obtained on the surface of the SET-failed device showed that many of the Sb atoms as well as some of the Ge atoms had diffused toward the region far away from the Mo electrodes. On the other hand, most of the Te atoms remained in the middle part of the GST. This suggests that device failure resulted in the out-diffusion of Sb atoms through SET and RESET processing, especially on the surface. The remaining GST system with less Sb was suggested to be one of the causes of the failure of the phase transition by SET and RESET.