External Article: Binary Oxide for Neuromorphic Circuits

Background

As Silicon(Si) has reached its material limitation, newer ways are being adapted to extend Moore’s law by

  • Changing the geometry(FINFET to Nanowire)
  • Using materials compatible with Silicon(eg. SiGe) for the FET channel to boost drive current while scaling down the node

Alongside, there is also an ongoing effort to find substitutes to Silicon(Si). III-V & SiC are promising and have already started displacing Si in applications for power switching, RF amplifiers, and optronics.

Also, there has been substantial work regarding the growth of III-V channel on Si[2][3]. Though pathbreaking, issues have cropped up in this mating due to lattice mismatch & growth techniques among others.

Silicon(Si) is also a material of choice for memory devices. Current memory devices store information based on the electronic charge trapped in an oxide or nitride[4][8][9]. This charge can leak with time, erasing the stored data.

 

Image result for charge based non volatile memory operation

Fig.1 Typical Floating(FG) memory and SONOS[4]

With neuromorphic computing and non-charge based storage being looked into pretty seriously, material substitutes are explored to silicon.

Research

The material under consideration is vanadium oxide(VO2) which exhibits Metal-Insulator Transition(MIT) ie. the material is an insulator at room temperature but starts to behave as a conductor at temperatures exceeding 68°C[6][12].

 

Related image

Fig.2 Metal-Insulator Transition(MIT) in VO2 [5]

 

This kind of material can be utilized for storing data and memory programming. They fall under the category of Phase Change Memory(PCM)[7]. Researchers at EPFL have used reactive magnetron sputtering to produce GexV1−xO2+y films which have a transition temperature of ~95°C[1][10][11][12].

 

Stacks Image 30

Fig.3 ON-OFF for VO2 based Switch[10]

Article

https://actu.epfl.ch/news/a-revolutionary-material-for-aerospace-and-neuromo/

Further Reading

A. Krammer et. al.,”Elevated transition temperature in Ge doped VO2 thin films”, Journal of Applied Physics 122, 045304, 2017

 

In the future, post optimization, vanadium oxide(VO2) based devices can be fabricated as a part of the CMOS backend flow owing to a low-temperature fabrication giving direct access to the memory cell using the on-chip transistor.

If you want to share your opinion kindly do so in the comments section or email me at u2d2tech@gmail.com.

References:

  1. C. Wu et. al., “Design of vanadium oxide structures with controllable electrical properties for energy applications”, Chem. Soc. Rev.,42, 5157-5183, 2013
  2. G. Duan et. al.,”Hybrid III-V on Silicon Lasers for Photonic Integrated Circuits on Silicon”,  IEEE Journal of Selected Topics in Quantum Electronics, Volume: 20, Issue: 4,  2014
  3. N. Zagni et. al., “Combined variability/sensitivity analysis in III-V and silicon FETs for future technological nodes”, Reliability Physics Symposium (IRPS), IEEE International, 2017
  4. J.Meena et.al.,”Overview of emerging nonvolatile memory technologies”, Nanoscale Research Letters, 9:526, 2014
  5. https://www.sciencedaily.com/releases/2015/04/150410165154.htm
  6. https://en.wikipedia.org/wiki/Vanadium(IV)_oxide
  7. https://en.wikipedia.org/wiki/Phase-change_memory
  8. https://en.wikipedia.org/wiki/Floating-gate_MOSFET
  9. https://en.wikipedia.org/wiki/Flash_memory
  10. https://phasechange-switch.org/
  11. https://publishing.aip.org/publishing/journal-highlights/new-oxide-and-semiconductor-combination-build-new-devices
  12. A. Krammer et. al.,”Elevated transition temperature in Ge doped VO2 thin films”, Journal of Applied Physics 122, 045304, 2017

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