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Fabrication and Characterization of Ultra-narrow RRAM Cells

Fabrication and Characterization of Ultra-narrow RRAM Cells. Byoungil Lee and H.-S. Philip Wong Electrical Engineering, Stanford University. Outline. Motivations AlOx RRAM typical cell characteristics Fabrication of ultra-narrow RRAM cells Characterization of ultra-narrow cells

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Fabrication and Characterization of Ultra-narrow RRAM Cells

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  1. Fabrication and Characterization of Ultra-narrow RRAM Cells Byoungil Lee and H.-S. Philip Wong Electrical Engineering, Stanford University

  2. Outline • Motivations • AlOx RRAM typical cell characteristics • Fabrication of ultra-narrow RRAM cells • Characterization of ultra-narrow cells • Summary and discussion

  3. Ultra-narrow RRAM Cells • Motivations • Issues with RRAM • Over-SET by over-shoot current. • Poor LRS uniformity, large reset current, and device failure. • Current-limiting devices are required. • Implementation of ‘Within-A-Cell-Current-Limiter’. • Study of scaling

  4. AlOx RRAM Large Cell • Bipolar switching. • Large variation in LRS and IRESET. w w W Pt TiN 10nm AlOx Pt

  5. AlOx RRAM Large Cell • Filamentary conduction property. • Does not scale with the size.

  6. AlOx RRAM Large Cell • Filamentary conduction property. • Does not scale with the size. • LRS and IRESET are determined by Ilimit

  7. IRESET ISET in RRAM

  8. Scaling Trend of RRAM • Filamentary conduction property. • No scaling with the size in the previous works. • LRS of our RRAM cell does scale with the size!

  9. Ultra-narrow RRAM Cell using ALD AlOx • Top-view SEM of the fabricated devices. • Smallest cell size: 50nm X 50nm w w 100nm

  10. Ultra-narrow RRAM Cell using ALD AlOx SiO2 AlOx Pt 10nm TiN Pt 20nm • Top Pt: 40nm, TiN: 40nm • Oxides thickness: 7.4 nm • Bottom Pt: 40nm • Metal width: 100nm • AlOx width: 10nm

  11. Process Flow Pt w TiN SiO2 Pt Pt AlOx TiN t Pt Pt SiO2 Pt TiN d SiO2 Pt Pt TiN SiO2 Pt

  12. DC I-V Characteristics • SET current is limited without any external current-limiters. • Due to resistive TiN layer and small contact area.

  13. Line Resistance • Current-limiting is not a result of the long electrode line. • New device features ‘Within-A-Cell-Current-Limiter.’

  14. Programming Cycle Test • 500nm standard cell shows a broad tail in LRS distribution. • Ultra-narrow cells truncate lower-end of LRS distribution.

  15. Scaling Trend of Ultra-narrow Cells • Filamentary conduction property. • IRESET and LRS does scale with the size!

  16. Programming Speed - SET/RESET: 30ns/1us - SET/RESET: 4ns/20ns

  17. Programming Endurance • 104 programming cycles.

  18. Summary • Demonstrated fabrication and characterization of ultra-narrow RRAM cells. • Established new aspect of scaling trend of filamentary conduction devices. • Within-A-Cell-Current-Limiter improves LRS distribution without integrating TRs.

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