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IC Fabrication

An integrated circuit is a miniature electronic circuit fabricated on a single crystal silicon wafer. It contains both active components like transistors and diodes and passive components like resistors and capacitors. The fabrication of ICs involves several processes like wafer preparation, oxidation, photolithography, diffusion, metallization, and testing. Photolithography is used to transfer circuit patterns onto each layer of the IC using a photomask, photoresist, exposure to light, and etching. The basic steps are repeated for each layer to build up the complete IC through patterning of doped regions, insulators, polysilicon, and metal layers. Major Indian fabrication facilities include Bharat Electronics Limited, SITAR, and Semiconductor

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Rajkumari Mishra
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447 views40 pages

IC Fabrication

An integrated circuit is a miniature electronic circuit fabricated on a single crystal silicon wafer. It contains both active components like transistors and diodes and passive components like resistors and capacitors. The fabrication of ICs involves several processes like wafer preparation, oxidation, photolithography, diffusion, metallization, and testing. Photolithography is used to transfer circuit patterns onto each layer of the IC using a photomask, photoresist, exposure to light, and etching. The basic steps are repeated for each layer to build up the complete IC through patterning of doped regions, insulators, polysilicon, and metal layers. Major Indian fabrication facilities include Bharat Electronics Limited, SITAR, and Semiconductor

Uploaded by

Rajkumari Mishra
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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IC Fabrication

GIDAYE GIRISH

1
INTEGRATED CIRCUITS

An integrated circuit (IC) is a miniature ,low


cost electronic circuit consisting of active and
passive components fabricated together on a
single crystal of silicon. The active components are
transistors and diodes and passive components are
resistors and capacitors.

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Advantages of integrated circuits
1. Miniaturization and hence increased equipment
density.
2. Cost reduction due to batch processing.
3. Increased system reliability due to the elimination
of soldered joints.
4. Improved functional performance.
5. Matched devices.
6. Increased operating speeds.
7. Reduction in power consumption

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IC Fabrication

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Basic processes involved in fabricating
Monolithic ICs
1. Silicon wafer (substrate) preparation
2. Epitaxial growth
3. Oxidation
4. Photolithography
5. Diffusion
6. Ion implantation
7. Isolation technique
8. Metallization
9. Assembly processing & packaging
10. Testing of packaged ICs

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Fab/Foundry
• Basic infrastructure – Clean room
( humidity & particle control),
Deionized water, nitrogen plant
• Processing equipment
• Testing facility
• Packaging facility – Wire bond, Die
bonding, encapsulation

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Basic components of an IC

• Active devices
Diodes, BJTs, JFETs, MOSFETs
• Passive components
Resistors, capacitors

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What is silicon
processing?
Process of growing, depositing
& patterning layers of different
materials

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Different layers comprising an IC

• Doped regions: Concentration and


type ( P/N)
Source, Drain, Collector, Base,
Emitter, Contacts
• Insulators: SiO2, Si3N4 – Gate oxide,
Passivation
• Polysilicon: Gate
• Metal: Al, Au, Silicides: Contacts,
Interconnects
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Lithography
Lithography: process used to transfer
patterns to each layer of the IC
Lithography sequence steps:
• Designer:
– Drawing the “layer” patterns on a layout
editor
• Silicon Foundry:
– Masks generation from the layer patterns
in the design data base
– Printing: transfer the mask pattern to the
wafer surface
– Process the wafer to physically pattern
each layer of the IC 20
Lithography
• The surface to be patterned is:
1. Photoresist coating
Photoresist

– spin-coated with photoresist


– the photoresist is dehydrated in an SiO2
Substrate
oven (photo resist: light-sensitive
organic polymer) 2. Exposure
Opaque Ultra violet light
• The photoresist is exposed to
ultra violet light: Mask

– For a positive photoresist exposed Unexposed Exposed


areas become soluble and non
exposed areas remain hard
• The soluble photoresist is Substrate

chemically removed 3. Development


(development).
– The patterned photoresist will now
serve as an etching mask for the Substrate
SiO2
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• The SiO2 is etched away
4. Etching
leaving the substrate
exposed:
– the patterned resist is used as
the etching mask
Substrate
• Ion Implantation:
– the substrate is subjected to 5. Ion implant

highly energized donor or


acceptor atoms
– The atoms impinge on the
surface and travel below it
– The patterned silicon SiO2 Substrate
serves as an implantation mask
6. After doping
• The doping is further driven
into the bulk by a thermal
cycle
diffusion Substrate

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•The lithographic sequence is
repeated for each physical layer used
to construct the IC. The sequence is
always the same:
–Photoresist application
–Printing (exposure)
–Development
–Etching

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Patterning a layer above the silicon surface
1. Polysilicon deposition 4. Photoresist development
Polysilicon

SiO2
Substrate Substrate
2. Photoresist coating 5. Polysilicon etching
photoresist

Substrate Substrate
3. Exposure UV light
6. Final polysilicon pattern

Substrate Substrate

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• Etching:
– Process of removing unprotected material
– Etching occurs in all directions
– Horizontal etching causes an under cut
– “preferential” etching can be used to minimize
the undercut
• Etching techniques:
– Wet etching: uses chemicals to remove the
unprotected materials
– Dry or plasma etching: uses ionized gases
rendered chemically active by an rf-generated
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plasma
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Fabs in our country

• Bharat Electronics Limited, Banglore


Bipolar process

• SITAR (ITI), Banglore

0.8 micron CMOS

• Semiconductor Complex Ltd, Chandigad

0.8 micron CMOS


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