Electrical current-induced gradual failure of crystalline Ge2Sb2Te5 for phase-change memory

Abstract

Electrical failure in crystalline Ge2Sb2Te5 was observed under a direct current bias, which induces a steady degradation of the electrical conductivity. This failure is induced by electromigration because alternating current bias stressing does not trigger this behavior. Nano-scaled voids were generated during current stressing, which explains the gradual increase in the quantitative resistance. Each nano-void previously comprised a molten phase that was induced by localized melting, which produced compositional variation during the solidification process. The phase-change memory can be damaged by electrical stressing in the non-active regions.

In situ TEM observation of void formation and migration in phase change memory devices with confined nanoscale Ge2Sb2Te5

“…The measured current density is much higher than the typical value for a line pattern structure of crystalline GST (∼1.8 MA cm −2 ) and high enough to drive the electric field-induced migration of the constituent elements of GST. 32 …”

New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

“…Line-patterned GST samples, which were 20 μm in length, 2 μm in width and 300 nm in thickness9, were subjected to an electric current or various temperatures. Thin films of GST were deposited using a DC magnetron sputterer on a 10-nm silicon oxide wafer and were patterned by photolithography using an aligner (Karl-Suss MA-6 II).…”

“…It is worth investigating MIT under electric current stressing conditions, i.e., more device-related characteristics. During the RcRAM operation (writing, erasing and reading), the cubic GST is exposed to various ranges of electric current stressing, and there is much evidence of changes in the structural and charge transport properties under these circumstances91011.…”

“…In contrast, a relatively low current density of approximately 10 6  A/cm 2 cannot generate the structural disorder need to transition to the insulating phase. The atomic displacement by a low current is negligible compared with that from a high current because the driving force is insufficient to generate a massive flux of atoms9. An electric current in the range of 10 6  A/cm 2 only assists in the rearrangement of vacancies.…”

RESET failure analysis of phase change memory based on Ge₂Sb₂Te₅

“…While phase transition processes are well understood, issues on performance and reliability are getting more and more attention in recent years, which makes the failure analysis of PCM becomes more and more important. Many efforts have been made to do the failure analysis, and the studies of PCM device failure are mainly focused on the electric-dependent experiments [6,7,8].…”