Summary
This is a variation of the TiOx standard recipe aimed to address volatility issues to otherwise non-volatile devices. It is realised as a thin AlOx layer introduced between the active layer and top electrode. The layer is thin enough as to amount as an interfacial modification rather that true bilayer devices. Devices exhibit lower volatility which eventually results in satisfactory multi-bit performance.
Process maturity: Stable
Active layer fabrication Data
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Fabrication method: |
Magnetron sputtering |
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Tool(s) used: |
Leybold HELIOS |
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Main fabrication params: |
Ar:O₂ ratio and flows; temperature (assumed RT if not specified); PBS (additional plasma source) enabled. Base Ar flow: 35 sccm. 2 kW for TiOx; 100 W for AlOx |
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Recipe |
Ar:O₂ |
PBS |
Temp |
Comments |
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TiOx: 8sccm_360_lambda |
4.4:1 |
Y |
25°C |
Deposition rate for AlOx is about 1 nm/10 mins. |
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AlOx: AlOx_100W |
4:1 (!) |
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TiOx: 8sccm_360_NoRF |
4.4:1 |
Y |
25°C |
Increased conductivity of the TiOx layer leads to easier forming. Most switching identified in the AlOx layer. |
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AlOx: AlOx_100W |
4:1 (!) |
Electrode configuration
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Top |
Bottom |
Tool |
Comments |
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Pt (12 nm) |
Ti/Pt (5/12 nm) |
LAB |
Standard recipe. Rectifying contacts when pristine or HRS, Ohmic when formed. |
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Pt (12 nm) |
Ti/Au (5/30 nm) |
LAB |
Bidirectional volatility. Base resistance high MΩ thickness dependent |
Indicative data
 |
 |
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Measurement: Pristine I-V characteristic (high resistivity TiOx; 4 nm AlOx) Device stack: Ti/Pt/TiOx/Pt 5/12/25/12 (in nm, bottom to top) Active layer recipe: 8sccm_360_lambda |
Measurement: I-V characteristic of a formed device (high resistivity TiOx; 4 nm AlOx) Device stack: Ti/Pt/TiOx/Pt 5/12/25/12 (in nm, bottom to top) Active layer recipe: 8sccm_360_lambda Comments: Gradual resistive change; analogue behaviour |
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Measurement: I-V characteristics of AlOx capped device (highly reduced TiOx; 4 nm AlOx) Device stack: Ti/Pt/TiOx/Pt 5/12/25/12 (in nm, bottom to top) Active layer recipe: 8sccm_360_NoRF Comments: Pristine devices; no forming |
