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Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 1
Chapter 2Introduction of IC
FabricationHong Xiao, Ph. D.
hxiao89@hotmail.com
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 2
Objectives
• Define yield and explain its importance
• Describe the basic structure of a cleanroom.
• Explain the importance of cleanroom protocols
• List four basic operations of IC processing
• Name at least six process bays in an IC fab
• Explain the purposes of chip packaging
• Describe the standard wire bonding and flip-chipbump bonding processes
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 3
Wafer Process Flow
Materials
Design
Masks
IC Fab
Test
Packaging
Final Test
ThermalProcesses
Photo-lithography
EtchPR strip
ImplantPR strip
Metallization CMPDielectricdeposition
Wafers
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 4
Fab Cost
• Fab cost is very high, > $1B for 8” fab
• Clean room
• Equipment, >$1M per tool
• Materials, high purity, ultra high purity
• Facilities
• People, training and pay
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 5
Wafer Yield
total
goodW Wafers
WafersY =
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 6
Die Yield
total
goodD Dies
DiesY =
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 7
Packaging Yield
total
goodC Chips
ChipsY =
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 8
Overall Yield
YT = YW×YD×YC
Overall Yield determines whether a fab ismaking profit or losing money
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 9
How Does Fab Make Money
• Cost:– Wafer (8”): ~$150/wafer*
– Processing: ~$200 (1$/wafer, 200 process steps)
– Packing: ~$1/chip
• Sale:– ~100 chips/wafer
– ~$50/chip (low-end microprocessor in 2000)
*Cost of wafer and price of chip are changing daily, numbersare choosing randomly based on general information.
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 10
How Does a Fab Make (Loss) Money
• 100% yield: 150+200+100 = $450/wafer
• 50% yield: 150+200+50 = $400/wafer
• 0% yield: 150+200 = $350/wafer
• 100% yield: 100××50 = $5,000/wafer
• 50% yield: 50×50 = $2,500/wafer
• 0% yield: 0×50 = $0.00/wafer
• 100% yield: 5000 - 450 = $4550/wafer
• 50% yield : 2500 - 400 = $2100/wafer
• 0% yield : 0 - 350 = − $350/wafer
Cost:
Sale:
ProfitMargin:
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 11
Throughput
• Number of wafers able to process– Fab: wafers/month (typically 10,000)
– Tool: wafers/hour (typically 60)
• At high yield, high throughput brought
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 12
Defects and Yield
nDAY
)1(
1
+∝
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 13
Yield and Die Size
Y = 28/32 = 87.5% Y = 2/6 = 33.3%
Killer Defects
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 14
Illustration of a Production Wafer
Test die
Die
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 15
Illustration of a Production Wafer
Scribe Lines
Dies
TestStructures
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 16
Clean Room
• Particles kills yield
• IC fabrication must in a clean room
• Artificial environment with low particle counts
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 17
Clean Room
• First used for surgery room to avoid bacteriacontamination
• Adopted in semiconductor industry in 1950
• Smaller device needs higher grade clean room
• Less particle, more expensive to build
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 18
Clean Room Class
• Class 10 is defined as less than 10 particleswith diameter larger than 0.5 µm per cubicfoot.
• Class 1 is defined as less than 1 such particlesper cubic foot.
• 0.18 mm device require higher than Class 1grade clean room.
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 19
Cleanroom Classes
0.1
1
10
100
1000
10000
100000
Class 100,000Class 10,000Class 1,000
Class 100
Class 10Class 1
# of
par
ticle
s /
ft3
0.1 1.0 10
Particle size in micron
Class M-1
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 20
Definition of Airborne ParticulateCleanliness Class per Fed. Std. 209E
Class
Particles/ft3
0.1 µm 0.2 µm 0.3 µm 0.5 µm 5 µm
M-1 9.8 2.12 0.865 0.28
1 35 7.5 3 1
10 350 75 30 10
100 750 300 100
1000 1000 7
10000 10000 70
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 21
Effect of Particles on Masks
Particleson Mask
Stumpon +PR
Hole on−PR
Film Film
Substrate Substrate
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 22
Effect of Particle Contamination
Partially Implanted Junctions
Particle
Ion Beam
Photoresist
Screen Oxide
Dopant in PR
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 23
Cleanroom Structure
Process Area
Equipment AreaClass 1000
Equipment AreaClass 1000
Raised Floorwith Grid Panels
Return Air
HEPA Filter
Fans
Pump, RFand etc.
ProcessTool
ProcessTool
Makeup Air Makeup Air
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 24
Gowning Area
Gown Racks
Benches
Shelf of Gloves, Hairand Shoe Covers Disposal Bins
Wash/CleanStations
Storage
Shelf ofGloves
Shelf ofGloves
Entrance
ToCleanroom
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 25
IC Fabrication Process Module
Photolithography
Thin film growth,dep. and/or CMP
Etching
PR Stripping PR Stripping
Ion Implantation
RTA or Diffusion
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 26
Illustration of Fab FloorProcess Bays
Gowning Area
Corridor
Equipment Areas
Sliding Doors
Service Area
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 27
Wet Processes
DryDryEtch, PR strip, or clean Rinse
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 28
Horizontal Furnace
Center Zone
Flat Zone
Distance
Temperature
Heating Coils
QuartzTube
Gas flow
Wafers
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 29
Vertical FurnaceProcessChamber
Wafers
Tower
Heaters
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 30
Schematic of a Track StepperIntegrated System
Hot Plates
PrepChamber
Chill Plates
Chill PlatesSpin Coater
Developer
Stepper
WaferMovement
Wafer
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 31
Cluster Tool with Etch and StripChambers
TransferChamber
PR StripChamber
Loading Station
EtchChamber
PR StripChamber
EtchChamber
Unloading Station
Robot
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 32
Cluster Tool with Dielectric CVDand Etchback Chambers
TransferChamber
Loading Station
PECVDChamber
O3-TOESChamber
Unloading Station
Robot
Ar SputteringChamber
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 33
Cluster Tool with PVD Chambers
TransferChamber
Loading Station
Ti/TiNChamber
Al⋅CuChamber
Unloading Station
Robot
Al⋅CuChamber
Ti/TiNChamber
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 34
Dry-in Dry-out CMP System
Wafer Loadingand Standby
Post-CMP Clean
Rinse
Dryer and WaferUnloading
Multi-head Polisher
PolishingPad
Clean Station
PolishingHeads
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 35
Process Bay and Equipment Areas
Process Area
Equ
ipm
ent A
rea
Equ
ipm
ent A
rea
Process Tools
Tab
les
For
PC
and
Met
rolo
gy T
ools
Service Area
Sliding Doors
Wafer Loading Doors
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 36
Test Results
Failed die
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 37
Chip-Bond Structure
Chip (Silicon)Chip BacksideMetallization
SolderSubstrateMetallization Substrate (Metal or Ceramic)
Microelectronics Devices and Circuits
Melt andCondense
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 38
Wire Bonding
Metal Wire
Formation ofmolten metal ball
Bonding Pad Bonding Pad Bonding Pad
Press to makecontact
Head retreat
Wire Clamp
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 39
Wire Bonding
LeadBonding Pad Bonding Pad Lead
Lead contact withpressure and heat
Clamp closed with heaton to break the wire
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 40
IC Chip with Bonding Pads
Bonding Pads
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 41
IC Chip Packaging
Pins
Chip
BondingPad
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 42
Chip with Bumps
Bumps
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 43
Flip Chip Packaging
Chip
Bumps
Socket Pins
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 44
Bump Contact
Chip
Bumps
Socket Pins
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 45
Heating and Bumps Melt
Chip
Bumps
Socket Pins
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 46
Flip Chip Packaging
Chip
Socket Pins
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 47
Molding Cavity for Plastic Packaging
Bonding Wires IC Chip
Lead Frame
PinsChip Bond Metallization
Top Chase
Bottom Chase
Molding Cavity
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 48
Ceramic Seal
Ceramic Cap
Bonding Wires IC Chip
Lead Frame, Layer 1
Pins
Cap SealMetallization
Chip Bond Metallization
Layer 2Layer 2
Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm 49
Summary
• Overall yield• Yield determines losing money or making
profit• Cleanroom and cleanroom protocols• Process bays• Process, equipment, and facility areas• Die test, wafer thinning, die separation, chip
packaging, and final test
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