Nano-Fab Simulator Layout - Sinclair Community College

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
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:
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
Example: Fabricating a MOSFET
• MOSFET = Metal-oxide-semiconductor field
effect transistor
MOSFET in Virtual NanoFab
The structure shown required about 25 steps.
User Operations
Thermal oxidation
Removing material
Wet etch
Dry etch
Depositing layers of material
Spin coat
E-beam evaporation
Chemical Vapor Deposition (CVD)
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
• 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
Note that resist above silicon is more fully
exposed than resist above aluminum.
Removing material
• Methods of removing material
– Wet etching
Immerse wafer in a bath of
liquid acid or solvent
– Dry etching
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
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.
titanium: adheres to
vertical surfaces as well as
Ion Implantation
• Modifies the electrical characteristics of the
silicon wafer: key to the operation of
semiconductor devices such as diodes and
• 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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