Transcript Photo-sensitive layer (“photoresist”)

Hello from Mike Deal at Stanford University - Senior Research
Scientist at the Stanford Nanofabrication Facility
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V5.15
Nanotechnology
“Nano” – From the Greek word for “dwarf” and means 10-9, or one-billionth.
Here it refers to one-billionth of a meter, or 1 nanometer (nm).
1 nanometer is about 3 atoms long.
“Nanotechnology” – Building and using materials, devices and machines at the
nanometer (atomic/molecular) scale.
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Nanostructures
Carbon nanotube
Gold/Silver nanoparticle
(U. Notre Dame)
Intel’s transistors used in their integrated
circuits (computer chips)
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How do you build something so small?
“Top-down” – building something by starting with a larger piece
and carving away material (like a sculpture).
“Bottom-up” – building something by putting together smaller
pieces (like building a car engine).
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Chemistry is important in both top-down and bottom-up processes
Bottom-up fabrication
• Adding atoms to atoms, molecules to molecules
• “Self-assembly” of atoms and molecules
• Use of chemical and biological processes
Current day examples:
Self-assemble of organic monolayers for
molecular transistors, etc. (Yale)
Vertical growth of nanowires for
electronic devices (Stanford)
Carbon
Nanotubes
More extreme example: Self-replicating robots.
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Top-down fabrication
Method used by integrated circuit industry to fabricate computer
chips down to ~ 15 nm size
• Makes use of depositing thin films, then “photolithography” and
plasma etching to make films into desired patterns on a silicon wafer.
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“Top-Down” nanofabrication
Silicon wafer
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Deposition equipment
Silicon wafer
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Deposition equipment
Gas phase reactants
Silicon wafer
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Deposition equipment
Gas phase reactants
SiN film
Silicon wafer
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SiN film
Silicon wafer
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Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Photolithography equipment
Light source
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Photolithography equipment
Light source
Ultraviolet light
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Photolithography equipment
Light source
Ultraviolet light
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Chemical developer
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Chemical developer
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Etching equipment
Plasma gas (etches film)
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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Etching equipment
Plasma gas (etches film)
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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SiN film
Silicon wafer
SiN thin film patterned correctly!
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With contamination present
Starting at photoresist step:
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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With contamination present
Dust particle
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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With contamination present
Light source
Ultraviolet light
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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With contamination present
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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With contamination present
Another dust particle
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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With contamination present
Plasma gas (etches film)
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
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With contamination present
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
SiN thin film patterned incorrectly!
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How do you build something so small?
-Requires very clean environment: “clean room”
0.5 micron wide
nanostructures
10-micron
particle
1-micron
particle
Human hair
60 microns
wide
~600X magnification
Relative size of clean room
contaminants
Magnified image of
contaminant on wafer
surface, which can cause
defects and failures in
nanostructures
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How do you build something so small?
-Requires very clean environment: “clean room”
• People wear clean room suits (also
called “gowns” or “bunny-suits)
• Huge fans circulate filtered air
throughout the facility
• Wafers are cleaned in liquid solutions
between every processing step
A lab user “gowning-up” in SNF
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Gregory Book and Swaminathan Rajaraman
(Swami) at Georgia Tech University
Greg Haugstad at University
of Minnesota
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