Effects of dopings on the electric-field-induced atomic migration and void formation in Ge2Sb2Te5

Electromigration in molten and crystalline Ge₂Sb₂Te₅ (GST) was characterized using pulsed DC stress to an isolated line structure. In the electomigration of molten GST, the effects of N-and Bi-doping on the electromigration were aslo studied to find the solution for inhibiting the electromigration. When a single pulse (~10^-3 s) was applied to the lines, both undoped and doped GST lines were melted by Joule heating, and Ge and Sb atoms migrate to the cathode, whereas Te atoms migrate to the anode. This elemental separation in the molten GST was caused by an electrostatic force-induced electromigration. The migration rate of the constituent atoms in the undoped GST was similar to that in Bi-doped GST, but was decreased by N-doping. Under applying a 10 MHz pulsed DC, the melting by Joule heating was inhibited, and electromigration in the crystalline state was detected. All constituent elements migrated to the cathode, which is originated from the electromigration by hole-windforce. This study provide the basic understanding about the degradation phenomena in phase change memory, and suggest the method for inhibiting the endurance failures.