Nanofabrication
• Nanofabrication manipulates very small materials (< 100 nm)
The size of an atom is
about 0.1 to 0.5 nm
The size of an apple is
about 7.0 to 8.3 cm
“…if an apple is magnified to the size of the earth, then the atoms in the apple are
approximately the size of the original apple.”
-- Richard Feynman
• Examples of nanofabrication
• Semiconductor chip in your smartphone and other electronics.
• Man made structures that mimic the nano-structures in Nature.
• Lab on a chip that shrinks clinic chemistry facilities into handheld
devices
The apple image downloaded from https://vq.vassar.edu/issues/2012/03/beyond-vassar/apple-a-day.html
Nanofabrication makes microelectronic chips
Transistor, the on/off switch
Apple A7 chip includes over 1 billion
transistors on a die 102 mm2 in size.
1138 nm
Transistor-Level Image of the Apple A7
Chipworks
Microelectronic chips have billions of nano-transistors
Phil. Trans. R. Soc. A (2012) 370, 3950–3972
Imagine building 1 billion houses, including their water, gas,
sewage, telephone lines, cables, roads, and highway
systems all on your finger nail. How would you do it?
Cu metallization characteristic of a six-level structure associated with a production 32bit RISC Processor in the CMOS 7S technology. (Courtesy of T Way, IBM
Microelectronics Division, Burlington, VT.)
The nanostructure on the butterfly wing can be mimicked using nanofabrication
Blue Morpho butterfly
Radwanul H. Siddiquea,
Karlsruhe Institute of Technology
proceedings.spiedigitallibrary.org
Rene Lopez, UNC at Chapel Hill
Journal of Vacuum Science & Technology B 30, 061802 (2012);
Nanofabrication can shrink clinical chemistry laboratories to the size of handheld devices
Clinical lab to handheld device
enabled by nanofabrication
http://www.royalwolverhamptonhospitals.nhs.uk/pathology_services/departments/clinical_chemistry.aspx
http://www.siliconsemiconductor.net/article/75748Commercialising-Lab-On-A-Chip-Technology.php
Nanofabrication is only limited by our imagination
http://www.zyvexlabs.com/EIPBNuG/EIPBN2007/2007.html
Photolithography:
A key process to make small things over large areas
Create a Designed pattern
on a transparent substrate
(Mask)
Put photoresist on wafers
Shine a light to change
the photoresist
The pattern replicated in
photoresist after developer wash
(Cartoons taken from ASML presentation slides)
Positive photoresist and negative photoresist
UV light
Mask blocks UV light at some areas
Photoresist only exposed where UV passes
Substrate
Light increases solubility in positive resist
Light decreases solubility in negative resist
How can light change a material’s solubility
Ionization
Electron in an excited state
or
n=3, E3
• Light is electromagnetic radiation
with energy Ep=h
n=2, E2
• Absorption of electromagnetic
radiation can move an electron to an
excited state, which may trigger a
chemical change.
n=1 , E1
Absorption of electromagnetic radiation
E = h
nucleus
Chm.1.1.3 Explain the emission of electromagnetic radiation in spectral form in terms of the Bohr model.
• When the electromagnetic radiation
is strong enough, the absorption of
the radiation can directly remove an
electron from the molecule, which is
a chemical change.
• The chemical changes can change
material’s solubility.
An example of positive photoresist
Photoresist before exposure
to UV light
+
Insoluble in base solution
UV light + H2O
Photoresist after exposure to
UV light
+
Soluble in base solution
An example of negative photoresist
All negative photoresists function by light induced cross-linking of a photosensitive agent.
By cross-linking the long polymer chain the solubility in the developer is reduced.
J. Chem. Educ., 1979, 56 (8), p 541
http://pubs.acs.org/doi/abs/10.1021/ed056p541