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Mikheil Mebonia PhD student at Ilia State, RWTH Aachen Universities and Forschungszentrum Jülich.
Electronic and thermoelectric properties of nanograiting layers
presented at 6-th Georgian-German School and Workshop in Basic Science (GGSWBS’ 14), July 2014, Tbilisi, Georgia
Advisors : Raphael Hermann (FZJ, University of Liege), Larissa Juschkin (FZJ, RWHT Aachen University ), Avtandil Tavkhelidze (Ilia State University)
When it happens ?
There will be two reflected waves. One reflected from the top of the indent and another from the bottom of the indent. If the depth a=λ/4 , where λ is electron de Broglie wavelength, two reflected waves will interfere destructively resulting in no reflected wave.
Nanograting (NG) improves thermoelectric and electron emission properties when the grating pitch becomes comparable with the electron’s de Broglie wavelength
Density of state (DOS) of nanograting layer
)(ρ0 EDOS in plane layer DOS in nanograting layer )ρ(E
where, G (H,w,a)>1 is a geometry factor.
Z
GEE /)(ρ)ρ( 0
Geometry induced doping or G-doping
Electron concentration n in the CB increases, which can be termed as geometry-induced electron doping or G-doping.
There are no ionized impurities.
G-doping is T-independent
J. Simon, V. Protasenko, C. Lian, H. Xing and D. Jena, , Science 327, 60-64 (2010).B. Yu, M. Zebarjadi, H. Wang, K. Lukas, H. Wang, D. Wang, C. Opeil, M. Dresselhaus, G. Chen, and Z. Ren, , Nano Lett. 12, 2077 (2012).
Process flow
Interference lithography
• Large-area periodic structures
• Large depth of focus
• Requires a coherent light
• Low cost – no complicated and expensive optics
• Ultimate resolution (half-pitch) for the wavelength ~λ/4
EUV: l = 11 nm feature size: ~3 nm
Possible scheme for IL
q1q2
S S‘
Resolution is limited by l/(sinq1+sinq2), max l/2.
No mask needed.
Lloyd mirror
• Ultimate resolution (half-pitch) for the wavelength ~λ/4
EUV LABORATORY EXPOSURE TOOLTechnical Specifications
Cleanroom class 100 (ISO 3) environment
Illumination scheme interference lithography
Accepts up to 100 mm wafer
Max. exposable area: 65 x 65 mm2
Single field: 2 x 2 mm2
EUV sensitive CCD camera
High precision positioners on all axes (encoder resolution < 10 nm)
Dose monitor for λ = 13.5 nm
LABORATORY-SCALED EUV SOURCESpectral Range and Technical Specifications
Pinch Radius 100 µm
Radiance: L ~ 100 W/(mm2sr) @ λ = 10,9 nm with 3,2% bandwidth
Electron/ion densities: n ~ 1017 cm−3
Temperature of plasma: Te ~ 35 eV Coherence length: lcoh ≈ 10-25 µm Triggered source >> repetition rate: up to 1,5
kHz
Gas Discharge Plasma Source for EUV Generation
PowerSupply
energystorage
f = j X B
I
switch
EXPERIMENTAL SETEUV Laboratory Exposure Tool
EUV Sourc
e
Dose Monito
r
Lithography Chamber
Loadlock
CCD Camer
a
Capacitive
Sensors
Mask holder and
Lithography Mask
Wafer holder
insid
e
EXPERIMENTAL SET-UPEUV Laboratory Exposure Tool
RIE facility in Physikzentrum
Reactive Ion Etcher Sentech SI 591 1M2
(SF6, CHF3, CF4, CH4, H2, N2)
Evacuated chamber
Etch gases flow in
Electrodes at top and bottom
Ionised gas
Adsorbed electrons create voltage drop from ion cloud to wafer
Ions are accelerated towards wafer
Review - Reactive Ion Etching
Review - Reactive Ion EtchingIon energy
pressure
Different etching mechanisms in Reactive Ion Etching
Physical (sputtering)
Chemical
Ion-assisted
We measure temperature and magnetic field dependence of• Resistivity • Thermal conductivity • Seebeck coefficient
Use van der Pauw technique 4 pont method to measure resistivity
Conclusion
* Make nanograiting on SOI wafer using XUV -IL
* Do ion etching
* Use CCMS to measure electrical and thermoelectric property
* Use AFM (Atomic force microscopy), scanning electron microscope (SEM) and ellipsometrie to measure properties of structured SOI wafer
* Different size of transmission mask to get less pitch size of structure
Thanks for your Attention!