Electromigration behaviors of Ge2Sb2Te5 chalcogenide thin films under DC bias

Yin Hsien Huang, Chi Hang Hang, Yu Jen Huang, Tsung-Eong Hsien*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Electromigration (EM) behaviors of pristine Ge2Sb 2Te5 (GST), nitrogen-doped GST (N-GST) and ceriumdoped GST (Ce-GST) thin-film strips under DC bias are presented. The mean-time-to-failure (MTTF) analysis based on the Black equation found that the EM failure times at room temperature are 1.2 × 104, 40 and 9.2 × 10 2 years and the activation energies (Ea) of EM process are 1.07, 0.57 and 0.68 eV for GST, N-GST and Ce-GST, respectively. Moreover, the calibration of the current density exponent, n, of Black's equation found n values are close to 2 for all samples, implying the dominance of grain boundary diffusion during the mass transport of EM process. For doped GSTs, the inferior EM failure lifespans and smaller Ea values were ascribed to the grain refinement effect which increases the number of grain boundaries in such samples. It consequently promoted the short-circuit diffusion and accelerated the EM failure in doped GSTs. The Blech-type tests on GSTs found that the threshold product, i.e., the product of current density and sample length ((j.L)th), is 200 A/cm for GST, 50 A/cm for N-GST and 66.67 A/cm for Ce-GST. Moreover, the product of diffusivity and effective charge number (i.e., DZ*) for GST, N-GST and Ce-GST was 2.0 × 10-7, 4.5 × 10-6 and 3.8 × 10-6 cm2/sec, respectively. Analytical results illustrated that the electrostatic force effect dominates the EM failure in samples with short strip lengths while the electron-wind force effect dominates the EM failure in samples with long strip lengths. Doping might alleviate the mass segregation in GST; however, its effect was moderate.

Original languageEnglish
Pages (from-to)449-456
Number of pages8
JournalJournal of Alloys and Compounds
Volume580
DOIs
StatePublished - 1 Jan 2013

Keywords

  • Black's theory
  • Blech structure
  • Chalcogenides
  • Electromigration
  • Phase-change random access memory

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