i) aproximación descendente ii) aproximación...
TRANSCRIPT
Bloque 4. Preparación de Nanomateriales
i) Aproximación Descendenteii) Aproximación Ascendente
Bloque 4: Preparación de Nanomateriales. Aproximación Descendente
Métodos Físico-QuímicosFotolitografía
Litografía de haz de electronesLitografía de nanoimpresión
Ciudad de Petra, 312 aC
Capital de los Nabateos
Aproximación de arriba-abajo (top-down)
Top-down
Botton-up
Litografía
AutoensamblajeSíntesis covalente
Estrategias para preparar Nanomateriales
Material Nanoestructurado
Herramientas en Nanotecnología
Bottom-up Top-down
Material Nanoestructurado Método descendenteMétodo ascendente
Método descendenteCrear objetos a partir de Macroobjetos
(Fotolitografía, nanolitografía,…)
Método ascendenteSíntesis Química-BioquímicaManipulación de átomos y
moléculas
Aproximación Descendente (top-down)
GraphenePotential
Applications
How Graphene can be synthesized?
exfoliation
Top-Down Bottom-up
CVD
Graphene
From GraphiteFrom carbon sources:
hydrocarbons, alcohols, carbon, ...
CVD: on Surface
polyethylene terephthalate (PET) substrate
Large Areas and transferred
Andrés Castellanos-Gómez, PhD Thesis 2011 UAM
Scotch tape exfoliation
Adhesivecontamination
Multilayergraphene
Few layergraphene
Graphene from Graphite: Micromechanical Exfoliation
Micromechanical Exfoliation with PDMS Stamps
Graphene from Graphite: Micromechanical Exfoliation
Micromechanical Exfoliation with PDMS Stamps
Andrés Castellanos-Gómez, PhD Thesis 2011 UAM
Graphene from Graphite: Micromechanical Exfoliation
Expansion of graphite
Graphene from Graphite: Chemical Exfoliation
Electrostatic repulsion prevent re-aggregation
water suspensionstable for weeks
Surfactantdificult to
detach
SDS
Increasedexfoliation x20
With
NaO
HW
ithout
NaO
H
NMP
Suspension stablefor weeks
Solvent expensive and with high boiling
point 4 mg/mL6 mg/mL
F. Zamora et al. work under patent
0
0,2
0,4
0,6
0,8
1
230 430 630 830
THF-Water (4:1) - 0.5 ml in 2 ml ofsolvents
Liquid phase exfoliation of Graphite massive production
c 0.1 g/L
NMP
4003002001000
8
7
6
5
4
3
2
1
0
X[nm]
Z[n
m]
4 nm
(a)
(b)
(c)
(d)
Fuji Dimatrix materials inkjet-printer DMP-2800
Potential use as ink for a comercial inkjet printer
1.41.210.80.60.40.20
2.5
2
1.5
1
0.5
0
X[µm]
Z[n
m]
2.5 nm
3.532.521.510.50
14
12
10
8
6
4
2
0
X[µm]
Z[n
m]
6 nm
F. Zamora et al. work under patent
ca. 6 layers
Thomas Swan graphene scale-up
Evolución de la Fotolitografía
100 nm
Miniaturización de objetos
El toro micrométrico de Kawata,
del tamaño de los glóbulos rojos,
ha sido obtenido mediante
fotopolimerización de una resina
(Nature 2001).
Fotolitografía
Current Silicon Technology
Basic NanotechnologyTri-Gate Transistors
14 nm node
Fotolitografía
Resolución en Fotolitografía
Optics - Basics and Diffraction
• Ray tracing (assuming light travels in straight lines) works well as long as the
dimensions are large compared to .
• At smaller dimensions, diffraction effects dominate.
• If the aperture is on the order of , the light spreads out after passing through
the aperture. (The smaller the aperture, the more it spreads out.)
small Plane wave
continues due to
superposition
Spherical
secondary
wavelets - same
More
spherical
propagation
Aperture -
fewer
wavelets
Huygens-Fresnel principle
Free space
Small
aperture
Proceso de Fabricación
Various lithography sources
Contact Proximity Projection
MFS = (d.)1/2 ~ MFS = ((d+g).)1/2 ~ MFS = 0.61 /NA ~
Modos de Litografía Óptica
• Resist is in contact with the mask: 1:1 magnification• Advantages: Inexpensive equipment, moderately high
resolution (~0.5 mm or better but limited by resist thickness- 0.1 mm demonstrated)
• Disadvantages: Contact with the mask degrades the mask that results in non-uniform resolution, no magnification.
Difracción dela luz limita R
d
Resist is not in contact with the mask: 1:1 magnification
Advantages: Inexpensive equipment Disadvantages: Low resolution (~1-2 mm).
Diffraction effects limit accuracy of pattern transfer. Less repeatable than contact methods, no magnification
Mask image is projected a distance from the mask and de-magnified to a smaller image: 1:4 -1:10 magnification
Advantages: High resolution (25-14 nm), No mask contact(high production compatible). Magnification.
Disadvantages: Extremely expensive and complicated equipment, diffraction effects limit accuracy of pattern transfer.
Paso a paso
Resolución en Fotolitografía
Photolithography
apply resist
mask alignment/
exposure
develop
etching
resist removal
Resumen del proceso
SubWavelength Lithography
• Beginning in ≈ 1998, chip manufacturers began to manufacture chips with feature sizes smaller than the wavelength of the light used to expose photoresist.
• This is possible because of the use of a variety of “tricks” - illumination system optimization, optical pattern correction (OPC) and phase shift mask techniques.
(From Synopsis Website - www.synopsis.com)
Current Lithographic Technology
193 nm Excimer Laser Source
Computer Console
Exposure Column(Lens)
Wafer
Reticle (Mask)
www.tnlc.ncsu.edu/information/ceremony/lithography.ppt
• Lenses are very effective and perfectly transparent for 193nm and above, so many are used
• A single “lens” may be up to 60 fused silica surfaces
• System maintained at atmospheric pressure
• Lens NA ~0.5-0.85
• Up to 1.1 for immersion
• Exposure field 26x32mm
• Steppers capable of >100300mm wafers per hourat >100 exposures per wafer
Immersion lithography
R= K1 /NA
• 45-nm node (ASML)
Hyper-NA Immersion Litho Tool
From 1 cm to 1 nm
Brattain and Bardeen's pnp point-contact germanium transistor operated as a speech amplifier with a power gain of 18 on December 23, 1947
www.lucent.com 1 cm
First Nanotubes based transistor based on a CNT. Dekker group 1998
Moore Low(1964)Number of transistors will double every 18 months
Tra
ns
isto
res
po
rc
m2
Año
45 nm level
Intel® Core™2 Quad
45 nm10 nm
SELF-ASSEMBLY
LITHOGRAPHY
CONVENCIONAL
LITHOGRAPHY
nanopatterns.png
10 nm1010 componentes/cm2
Producción en laboratorio : 14 nm de sección de canal
Nanotecnología Básica
Current Silicium Technology
Basic NanotechnologyTri-Gate Transistors
14 nm node
Litografía de haz de electrones
Diferencias con la Litografía Óptica:
Longitud de onda de los electrones es menor
Los electrones presentan difracción despreciable (algo de scattering en la
resina)
Procedimiento de fabricación lento: no útil en producción
• Ventajas Mejor resolución
Escritura directa, sin mascara
Tamaño, forma y arquitectura arbitraria
• Inconvenientes Producción en serie
Areas pequeñas y lento
Scattering
Compatibilidad
Litografía de haz de electrones
• Fuente: electrones
• Voltage de aceleración Vc=120kV, λ=0.0336Å
• Utiliza una columna de electrones para generar
el haz
Litografía de haz de electrones
• Similar techniques to optical lithography: projection-printing
• Beam diameter 5 nm
• Can achieve a resolution of about 10 nm
• Limitation: secondary electrons…
surface gated quantum dot device
with submicron airbridge on
GaAs/AlGaAs
Litografía de haz de electrones
• (a) Sample is coated with a thin layer of a
polymer chemical known as the resist (ei.
polymethylmethacrylate, PMMA).
• (b) With EBL, there must be a path to ground for
the electrons. Thus, a small section of the
PMMA must be scraped away on the edge of the
sample so that conductive tape can be attached
from the sample to the stage (ground). If the
sample itself is an insulator, a very thin (10-20 Å)
layer of gold must be deposited onto the PMMA.
• (b) PMMA breaks down into smaller
molecular weight monomers upon exposure
to electrons. Afterwards, the exposed regions
can be rinsed away (developed) using a
chemical known as methyl-isobutyl-ketone.
• The rest is like optical lithography
Litografía de haz de electrones (EBL)
PMMA-polymetracrilato
Columna de electrones
Litografía de nanoimpresión
Preparación del sello
Impresión de patrones vía modo-estampa pre-diseñado
Polydimethylsiloxane (PDMS)
(a)(b) (c)
Stable for months
Nano-printing technology
• Si Stamp by e-beam lithography
• Polydimethylsiloxan (PDMS) stamp mat.
• OR add “ink” containing thiol molecules
• print on Si/ Au demosnstrated
• Structured SAM on Si/ Au (50 nm)
• Resolution depends on stamp and ink
Imprint mold with 10nm
diameter pillars
10nm diameter holes imprinted in
PMMA
10nm diameter metal dots fabricated
by NIL
Nanolitografía
Scanning Probe Lithography
• Probe
STM, AFM
• Techniques
Voltage pulse
CVD
Local electrodeposition
Dip-pen
Microscopias de Campo Cercano
Herramientas para la Nanotecnología
Scanning Tunnel
Microscope (STM)
Atomic Force
Microscope (AFM)
460nm
Ver
Manipular - Organizar
Medir Propiedades
Microscopio de Fuerzas Atómica (AFM)
(palanca)
(punta)
10-20 nm
Escribiendo con STM
• Examples of STM built
nanostructures with atom dragging
• Quantum corrals (diameter 14nm)
• Chains of atoms…other more
complex structures
• Ultimate in terms of resolution—
costly—slow
88
• Other tool is the Atomic force microscope
• The force between the cantilever and the sample is used to probe the
topography on the sample. Several modes of imaging to discuss later…
• Use conductive tip AFM as electron source for e-beam lithography
• Sub 50nm in commercial e-beam resist demonstrated
• SPM-based e-beam: less backscatter electrons
Quate and collaborators (Stanford)
Escribiendo con AFM
Dip Pen Lithography
90
AFM Dip Pen Lithography
• AFM tip is used to deliver molecules (Solvent meniscus)
• Naturally forms in the ambient atmosphere.
• Molecules anchor themselves to the substrate via
chemisorption
• Features as small as 15 nm linewidths
• and ~ 5 nm spatial resolution
• Chemical patterning of this sort can have a number of
applications
• Patterning conducting molecules, selective sites for
reactions, ….
Murkin Group