Nano-Fab Simulator Layout - Sinclair Community College

Report
Virtual NanoFab
A Silicon NanoFabrication Trainer
Nick Reeder, Sinclair Community College
Andrew Sarangan, University of Dayton
Jamshid Moradmand, Sinclair Community College
Challenge: Providing Hands-on Silicon
Nanofabrication Experience
• The facilities needed to do silicon nanofab
are very expensive.
Solution: Virtual Nanofab
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Software that we’re developing to teach
students about the steps involved in processing
a silicon wafer.
Please take a copy of the installation disc!
System Requirements:
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Operating system: Windows XP or higher
Memory: 2 GB RAM
Hard drive: 300 MB of free space
If your computer does not have National Instruments
LabVIEW installed, you must install the free LabVIEW
run-time engine, which is included on the installation
disc.
Example: Fabricating a MOSFET
• MOSFET = Metal-oxide-semiconductor field
effect transistor
MOSFET in Virtual NanoFab
The structure shown required about 25 steps.
User Operations
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Thermal oxidation
Photolithography
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Removing material
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Wet etch
Dry etch
Depositing layers of material
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Spin coat
Mask
Expose
Develop
E-beam evaporation
Chemical Vapor Deposition (CVD)
Sputtering
Ion implantation (“doping”)
Thermal Oxidation
• Grows a layer of silicon dioxide (SiO2) on the
wafer surface.
• Key properties of SiO2:
– Impervious to ion implantation.
– Can be etched away by immersion in hydrofluoric
acid (HF), which does not etch silicon.
Thermal Oxidation in Virtual NanoFab
Photolithography
• Steps in photolithography:
– Spin-coat photoresist.
– Create and place mask. Mask defines which
areas will be exposed to UV light and which areas
will be shaded.
– Expose with UV light.
– “Develop” the photoresist: UV-exposed areas are
removed, while shaded areas remain.
Photolithography in Virtual NanoFab
1. Before exposing:
2. After exposing (but before developing):
3. After developing:
Exposure with Uneven Layer
Thicknesses
Note that resist above silicon is more fully
exposed than resist above aluminum.
Removing material
• Methods of removing material
– Wet etching
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Low-tech
Immerse wafer in a bath of
liquid acid or solvent
– Dry etching
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High-tech
Expose wafer to plasma beam
Etching in Virtual NanoFab
SiO2 (blue) after wet
etch with hydrofluoric
acid: note tapered
sidewalls and undercut
of photoresist (pink).
SiO2 after dry etch with
CF4 plasma: note vertical
sidewalls.
Depositing Layers
• Methods of depositing materials
– Electron-beam evaporation
– Chemical vapor deposition (CVD)
– Sputtering
Deposition in Virtual NanoFab
Evaporated titanium
(gray): accumulates only
on horizontal surfaces.
Chemical-vapor-deposited
titanium: adheres to
vertical surfaces as well as
horizontal.
Ion Implantation
• Modifies the electrical characteristics of the
silicon wafer: key to the operation of
semiconductor devices such as diodes and
transistors.
• Implanting boron results
in “p-type” doping.
• Implanting phosphorus
results in “n-type” doping.
Ion Implantation in Virtual NanoFab
Other Features
• Maintains history of user operations.
• “Reference & Videos” page provides chapters
explaining theory, along with videos of
operations being performed in the lab.

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