Introduction to Wafer fabrication
Process
Presented by
Asst.Prof. Dr. Rardchawadee Silapunt
Outlines
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Clean room
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Wafer Fab Process
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Outlines
1
Clean room
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Clean Room @ TMEC
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It took time to install cleanroom
PLAY MOVIE
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Outlines
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Wafer Fab Process
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Processing line @ TMEC
Cleaning Process
Implanter
Dry Etching
Furnace
Photolithography
Down to 0.5μm
Technology
Metrology
Plasma CVD
Sputtering
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Overview to Lithography process
What is Lithography Process?
The word come from the Greek “Lithos” and “Graphia”
Lithos = Stones , Graphia = to write
It means “ Writing on stones”.
In Semiconductor, stones are Silicon wafers and our patterns are written with a
light-sensitive polymer called “Photoresist”
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Overview to Lithography process
9 Steps of Lithography process.
1. Wafer preparation
2. Coat with Photoresist
5. Post-Exposure Bake (PEB)
6. Development
7. Postbake, Hardbake
3. Prebake, Softbake
8. Etch or Implant
4. Align and Exposure
9. Photoresist strip
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Photolithography Problem
Light Diffraction is occur during
photolithography process.
OPC patterns are used to reduce the error in
photolithography process.
Without OPC
With OPC
(a)
(b)
(c)
(d)
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How to patterning circuit
Processing
- Film Deposition
- Photolithography
- Etching
- Implantation
Wafer
Integrated Circuit (IC)
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Processing line
Silicon Wafer
p-type wafer
p-type
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Film Deposition
SiO2
Initial oxidation: O2/H2 (Thickness: 420 nm)
p-type
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Photolithography
Coater
Stepper
Developer
Photoresist (PR)
p-type
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Processing line
Photoresist Characteristic
PR is made up of a resin R, the photoactive compound M, the solvent S, and component
appears during exposure which are exposure products P.
The exposure products generated by the reaction of M with UV light.!!
Applying Beer’s Law, the absorption coefficient  is then,
M0 = initial PAC concentration (non-exposed)
A = bleachable absorption coefficients of
Dill parameters
B = Non-bleachable absorption coefficients of
Dill parameters
Other non-bleachable components of the PR such
as dye are added to B
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Processing line
Dill Paramaters of Photoresist
Where several assumptions are made in solving this differential equation and I x t is the
optical dose. If D is the resist thickness, the Dill parameters can be measured by:
T(∞)
is transmittance at the
air-resist interface
T(0)
T(0) is the transmittance of the unexposed resist, and
T(∞) is the transmittance of the completely exposed resist
is the initial slope of the transmittance vs dose curve
Two transmittance curves for Kodak 820 resist 365 nm. The curves are for a convection oven post-apply bake of 30 minutes at the
temperatures shown
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Etching
Simulation of Plasma Etching
Photoresist (PR)
Dry etch oxide
p-type
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Etching
Directionality of Etcing Process
Isotropic Etch
Directional Etch
Vertical Etch
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Etching
Two Kinds of Etching Method
Wet Etching
- by Wet chemical solution
- Isotropic etching
Vertical E/R ~ Horizontal E/R Pure
Chemical Reaction High
Selectivity CD Loss or Gain
Dry Etching
- by Plasma
- Anisotropic etching
Vertical E/R >> Horizontal E/R
Ion assisted Relatively low
Selectivity No CD bias
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Implantation
n-well implantation : Phosphorus
Photoresist (PR)
p-type
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Chemical Mechanical Planarization (CMP)
CMP removes material from uneven topography on a wafer surface until
a flat (planarized) surface is created.
CMP combines the chemical removal effect of an acidic or basic fluid solution with
the "mechanical" effect provided by polishing with an abrasive material.
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Processing line
How to patterning a CMOS !!!
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