Investigating the switching mechanism of interfacial phase change memory
Abstract/Contents
- Abstract
- Phase Change Memory (PCM) is a leading candidate for next generation data storage, but it typically suffers from high switching (RESET) current density (20--30 MA/cm2). Interfacial Phase Change Memory (IPCM) is a type of PCM using multilayers of Sb2Te3/GeTe, with up to 100× lower reported RESET current compared to the standard Ge2Sb2Te5-based PCM. Several hypotheses involving fundamentally new switching mechanisms have been proposed to explain the low switching current densities, but consensus is lacking. IPCM switching is investigated by analyzing its thermal, electrical, and fabrication dependencies. First, the effective thermal conductivity (∼0.4 Wm−1K−1) and thermal boundary resistance (∼3.4 m2KGW−1) of Sb2Te3/GeTe multilayers is measured. Simulations show that IPCM thermal properties account only for ∼13% reduction of current vs standard PCM and cannot explain previously reported results. Interestingly, electrical measurements reveal that IPCM RESET indeed occurs by a melt-quench process, similar to PCM. High deposition temperatures are shown to cause defects including surface roughness and voids within the multilayer films. Thus, the substantial RESET current reduction of IPCM appears to be caused by voids within the multilayers, which migrate to the bottom electrode interface by thermophoresis, reducing the effective contact area. These results shed light on the IPCM switching mechanism, suggesting that an improved control of layer deposition is necessary to obtain reliable switching. Finally, finite element simulations are performed to predict time and volumetric scaling trends of PCM switching. Usage of pulse widths beyond a few nanoseconds are shown to be essentially wasting energy due to the time scales of device heating and is experimentally verified. Finally, current densities are predicted to become worse at ultra-scaled dimensions (bottom electrode diameter < ~10 nm) due to thermal and current confinement problems.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2019; ©2019 |
| Publication date | 2019; 2019 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Okabe, Kye Loren |
|---|---|
| Degree supervisor | Wong, Hon-Sum Philip, 1959- |
| Thesis advisor | Wong, Hon-Sum Philip, 1959- |
| Thesis advisor | Pop, Eric |
| Thesis advisor | Saraswat, Krishna |
| Degree committee member | Pop, Eric |
| Degree committee member | Saraswat, Krishna |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Kye Loren Okabe. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2019. |
| Location | https://purl.stanford.edu/gd855zg9867 |
Access conditions
- Copyright
- © 2019 by Kye Loren Okabe
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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