Transcript Wafer Manufacturing

Fabrication Laboratory
Spring 2012
References
• Handout
• J.D. Plummer, M.D. Deal, and P.B. Griffin, Silicon VLSI Technology:
Fundamentals, Practice and Modeling, Prentice-Hall, 1st Ed., 2001.
• H. Xiao, Introduction to Semiconductor Manufacturing Technology,
Prentice Hall, 1st Ed., 2001.
• S.K. Ghandhi, VLSI Fabrication Principles: Silicon and Gallium
Arsenide, John Wiley & Sons, 2nd Ed., 1994.
• P. van Zant, Microchip Fabrication, McGraw-Hill, 4th Ed., 2000.
• S.M. Sze, VLSI Fabrication, McGraw-Hill, 2nd Ed., 1988.
• Y. Tsividis, Operation and Modeling of The MOS Transistor, Oxford
University Press, 2nd Ed., 1999.
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Grading
• 40% final exam
• 40% experimental expertise
• 20% project
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Introduction to Device
Fabrication
Farshid Karbassian
Outline
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Historical Overview
Wafer Manufacturing
Cleanroom Technology
Fabrication Process
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Thermal Oxidation
Deposition
Photolithography
Etching
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Historical Overview
First Transistor
Bell Laboratory-1947
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Historical Overview
Nobel Prize in Physics (1956)
“for their research on semiconductors and their
discovery of the transistor effect”
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Historical Overview
Invention of Integrated Circuits
Texas Instruments-1958
Fairchild-1959
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Historical Overview
Nobel Prize in Physics (2000)
“For basic work on information and communication technology”
“for developing semiconductor heterostructures used in
high-speed and optoelectronics”
“for his part in the invention of
the integrated circuit”
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Historical Overview
Today's Integrated Circuits
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Historical Overview
Moore’s Law
• The number of transistors on a chip
doubles
roughly
every two
years.
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Historical Overview
Scaling
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Historical Overview
New Structures
• Tri-gate Transistor
• FinFET
• CNTFET
V. Iyengar, et al. IEEE Trans. Electron Devices 54 1177 (2007)
H. Sellier, et al. Phys. Rev. Lett. 97 206805 (2006)
A. Javey, et al. Nature 424 654 (2003)
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Wafer Manufacturing
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Wafer Manufacturing
Why Silicon?
• About 25.7% of the earth’s crust is silicon.
• Si raw material can be found anywhere in
large quantities.
• Crystallization of Si is much cheaper than
any other semiconductor material.
• SiO2
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Wafer Manufacturing
Crystal Pulling
• Czochralski Crystal Growth
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Wafer Manufacturing
Slicing
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Wafer Manufacturing
Lapping, Etching and Polishing
• To remove
damages caused
by slicing
several steps
are performed
so that wafers
with one mirror
finish will
obtain.
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Cleanrooms,Wafer cleaning &
Gettering
• Modern IC factories employ a three
tiered approach to control unwanted
impurities:
• Clean factories
• Wafer cleaning
• Gettering
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Cleanrooms
• Fab process is done
in an environment called
cleanroom.
• A cleanroom is
identified by a class
number which shows
how clean it is.
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RCA cleaning
• RCA I
NH4OH:H2O2:H2O 1:1:5 – 1:2:7 (70-80OC)
• DI water
• RCA II
HCl:H2O2:H2O 1:1:6 – 1:2:8 (70-80OC)
• DI water
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Thermal Oxidation
• At high temperature O2 molecules diffuse
across an existing oxide layer to reach the
Si/SiO2 interface.
• Oxidation is also
used for device
isolation.
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Deposition
• Deposition is a necessary step in the
fabrication technology.
p-type Si substrate
SiO2
gate material (polysilicon)
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Patterning
p-type Si substrate
SiO2
UV
polysilicon
metal
photoresist
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Photolithography
UV Light

HMD
S
Resist
Mask

1) Vapor prime
2) Spin coat
3) Soft bake
4) Alignment
and Exposure
5) Post-exposure
bake
6) Develop
7) Hard bake
8) Develop inspect
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Dopant
Diffusion
Dopant
T
Silicon
Junction depth
Silicon
O2
Samples
Coil
POCl3
n+ polysilicon
n+
n+
p-type Si
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Finished chips
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Dicing
• Samples are ready
to dice now.
• After dicing, gold wires
are bonded to the chips,
and then they are
packed.
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Bonding
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Bonding
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Packaging
• Types of packages:
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Simulation
• Process Simulation
• Device Simulation
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Any questions?