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Nanoscale Observations of the Operational Failure for Phase-change-type Nonvolatile Memory Devices using Ge2Sb2Te5 Chalcogenide Thin Films
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- Authors
- Sung-Min Yoon, Kyu-Jeong Choi, Nam-Yeal Lee, Seung-Yun Lee, Young-Sam Park, Byoung-Gon Yu
- Issue Date
- 2007-10
- Citation
- Applied Surface Science, v.254, no.1, pp.316-320
- ISSN
- 0169-4332
- Publisher
- Elsevier Science, Elsevier
- Language
- English
- Type
- Journal Article
- Abstract
- In this study, a phase-change memory device was fabricated and the origin of device failure mode was examined using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Ge 2 Sb 2 Te 5 (GST) was used as the active phase-change material in the memory device and the active pore size was designed to be 0.5μ m. After the programming signals of more than 2 × 1 0 6 cycles were repeatedly applied to the device, the high-resistance memory state (reset) could not be rewritten and the cell resistance was fixed at the low-resistance state (set). Based on TEM and EDS studies, Sb excess and Ge deficiency in the device operating region had a strong effect on device reliability, especially under endurance-demanding conditions. An abnormal segregation and oxidation of Ge also was observed in the region between the device operating and inactive peripheral regions. To guarantee an data endurability of more than 1 × 1 0 10 cycles of PRAM, it is very important to develop phase-change materials with more stable compositions and to reduce the current required for programming. © 2007 Elsevier B.V. All rights reserved.