Introduction of IC Fabrication - Advanced Silicon Device and
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Chapter 2 Introduction of IC Fabrication Hong Xiao, Ph. D. hxiao89@hotmail.com Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 1 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-chip bump bonding processes Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 2 Wafer Process Flow Materials IC Fab Metallization CMP Dielectric deposition Test Wafers Thermal Processes Implant PR strip Etch PR strip Packaging Masks Photolithography Final Test Design Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 3 Fab Cost • • • • • • Fab cost is very high, > $1B for 8” fab Clean room Equipment, usually > $1M per tool Materials, high purity, ultra high purity Facilities People, training and pay Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 4 Wafer Yield YW Hong Xiao, Ph. D. Wafers good Waferstotal www2.austin.cc.tx.us/HongXiao/Boo k.htm 5 Die Yield YD Hong Xiao, Ph. D. Dies good Diestotal www2.austin.cc.tx.us/HongXiao/Boo k.htm 6 Packaging Yield YC Hong Xiao, Ph. D. Chips good Chips total www2.austin.cc.tx.us/HongXiao/Boo k.htm 7 Overall Yield YT = YWYDYC Overall Yield determines whether a fab is making profit or losing money Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 8 How Does Fab Make (Loss) Money • Cost: – Wafer (8”): ~$150/wafer* – Processing: ~$1200 ($2/wafer/step, 600 steps) – Packing: ~$5/chip • Sale: – ~200 chips/wafer – ~$50/chip (low-end microprocessor in 2000) *Cost of wafer, chips per wafer, and price of chip varies, numbers here are choosing randomly based on general information. Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 9 How Does a Fab Make (Loss) Money Cost: • 100% yield: 150+1200+1000 = $2350/wafer • 50% yield: 150+1200+500 = $1850/wafer • 0% yield: 150+1200 = $1350/wafer Sale: • 100% yield: 20050 = $10,000/wafer • 50% yield: 10050 = $5,000/wafer • 0% yield: 050 = $0.00/wafer • 100% yield: 10000 - 2350 = $7650/wafer Profit • 50% yield : 5000 - 1850 = $3150/wafer Margin: • 0% yield : 0 - 1350 = - $1350/wafer Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 10 Question • If yield for every process step is 99%, what is the overall processing yield after 600 process steps? Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 11 Answer • It equals to 99% times 99% 600 times • 0.99600 = 0.0024 = 0.24% • Almost no yield Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 12 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/Boo k.htm 13 Defects and Yield 1 Y n (1 DA) Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 14 Yield and Die Size Killer Defects Y = 28/32 = 87.5% Hong Xiao, Ph. D. Y = 2/6 = 33.3% www2.austin.cc.tx.us/HongXiao/Boo k.htm 15 Illustration of a Production Wafer Die Test die Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 16 Illustration of a Production Wafer Test Structures Scribe Lines Dies Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 17 Clean Room • Artificial environment with low particle counts • Started in medical application for post-surgery infection prevention • Particles kills yield • IC fabrication must in a clean room Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 18 Clean Room • First used for surgery room to avoid bacteria contamination • 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/Boo k.htm 19 Clean Room Class • Class 10 is defined as less than 10 particles with diameter larger than 0.5 mm per cubic foot. • Class 1 is defined as less than 1 such particles per cubic foot. • 0.18 mm device require higher than Class 1 grade clean room. Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 20 Cleanroom Classes 100000 # of particles / ft3 10000 1000 100 10 1 0.1 Hong Xiao, Ph. D. 0.1 1.0 10 Particle size in micron www2.austin.cc.tx.us/HongXiao/Boo k.htm 21 Definition of Airborne Particulate Cleanliness Class per Fed. Std. 209E Particles/ft3 Class 0.1 mm 0.2 mm 0.3 mm 0.5 mm M-1 9.8 2.12 0.865 0.28 1 35 7.5 3 1 10 350 75 30 10 750 300 100 100 5 mm 1000 1000 7 10000 10000 70 Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 22 Effect of Particles on Masks Particles on Mask Stump on +PR Hong Xiao, Ph. D. Hole on -PR Film Film Substrate Substrate www2.austin.cc.tx.us/HongXiao/Boo k.htm 23 Effect of Particle Contamination Ion Beam Dopant in PR Particle Photoresist Screen Oxide Hong Xiao, Ph. D. Partially Implanted Junctions www2.austin.cc.tx.us/HongXiao/Boo k.htm 24 Cleanroom Structure Makeup Air Makeup Air Fans Equipment Area Class 1000 Process Tool Return Air Hong Xiao, Ph. D. HEPA Filter Class 1 Process Area Equipment Area Class 1000 Process Tool Raised Floor with Grid Panels www2.austin.cc.tx.us/HongXiao/Boo k.htm Pump, RF and etc. 25 Mini-environment • Class 1000 cleanroom, lower cost • Boardroom arrangement, no walls between process and equipment • Better than class 1 environment around wafers and the process tools • Automatic wafer transfer between process tools Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 26 Mini-Environment Cleanroom Makeup Air Makeup Air Fans HEPA Filter HEPA Filter < Class 1 Class 1000 Process Tool Return Air Hong Xiao, Ph. D. Class 1000 Raised Floor with Grid Panels www2.austin.cc.tx.us/HongXiao/Boo k.htm Process Tool Pump, RF and etc. 27 Gowning Area Shelf of Gloves, Hair and Shoe Covers Gown Racks Entrance Disposal Bins Shelf of Gloves To Cleanroom Wash/Clean Stations Shelf of Gloves Storage Benches Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 28 IC Fabrication Process Module Thin film growth, dep. and/or CMP Photolithography Etching Ion Implantation PR Stripping PR Stripping RTA or Diffusion Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 29 Illustration of Fab Floor Equipment Areas Process Bays Corridor Service Area Sliding Doors Hong Xiao, Ph. D. Gowning Area www2.austin.cc.tx.us/HongXiao/Boo k.htm 30 Mini-environment Fab Floor Process and metrology tools Service Area Emergency Exits Hong Xiao, Ph. D. Gowning Area www2.austin.cc.tx.us/HongXiao/Boo k.htm 31 Wet Processes Etch, PR strip, or clean Hong Xiao, Ph. D. Rinse www2.austin.cc.tx.us/HongXiao/Boo k.htm Dry 32 Horizontal Furnace Heating Coils Wafers Quartz Tube Temperature Gas flow Center Zone Flat Zone Distance Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 33 Vertical Furnace Process Chamber Heaters Wafers Tower Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 34 Schematic of a Track Stepper Integrated System Wafer Prep Chamber Spin Coater Chill Plates Stepper Chill Plates Hong Xiao, Ph. D. Developer Hot Plates www2.austin.cc.tx.us/HongXiao/Boo k.htm Wafer Movement 35 Cluster Tool with Etch and Strip Chambers PR Strip Chamber PR Strip Chamber Etch Chamber Etch Chamber Transfer Chamber Robot Loading Station Hong Xiao, Ph. D. Unloading Station www2.austin.cc.tx.us/HongXiao/Boo k.htm 36 Cluster Tool with Dielectric CVD and Etchback Chambers O3-TOES Chamber Ar Sputtering Chamber PECVD Chamber Transfer Chamber Robot Loading Station Hong Xiao, Ph. D. Unloading Station www2.austin.cc.tx.us/HongXiao/Boo k.htm 37 Cluster Tool with PVD Chambers AlCu Chamber AlCu Chamber Ti/TiN Chamber Ti/TiN Chamber Transfer Chamber Robot Loading Station Hong Xiao, Ph. D. Unloading Station www2.austin.cc.tx.us/HongXiao/Boo k.htm 38 Dry-in Dry-out CMP System Wafer Loading and Standby Polishing Pad Post-CMP Clean Polishing Heads Rinse Multi-head Polisher Dryer and Wafer Unloading Clean Station Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 39 Process Bay and Equipment Areas Sliding Doors Process Area Equipment Area Equipment Area Tables For PC and Metrology Tools Process Tools Service Area Wafer Loading Doors Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 40 Test Results Failed die Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 41 Chip-Bond Structure Microelectronics Devices and Circuits Chip Backside Metallization Chip (Silicon) Solder Substrate Metallization Hong Xiao, Ph. D. Melt and Condense Substrate (Metal or Ceramic) www2.austin.cc.tx.us/HongXiao/Boo k.htm 42 Wire Bonding Metal Wire Wire Clamp Bonding Pad Bonding Pad Bonding Pad Formation of molten metal ball Press to make contact Head retreat Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 43 Wire Bonding Bonding Pad Lead Lead contact with pressure and heat Hong Xiao, Ph. D. Bonding Pad Lead Clamp closed with heat on to break the wire www2.austin.cc.tx.us/HongXiao/Boo k.htm 44 IC Chip with Bonding Pads Bonding Pads Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 45 IC Chip Packaging Chip Bonding Pad Pins Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 46 Chip with Bumps Bumps Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 47 Flip Chip Packaging Bumps Chip Socket Hong Xiao, Ph. D. Pins www2.austin.cc.tx.us/HongXiao/Boo k.htm 48 Bump Contact Bumps Chip Socket Hong Xiao, Ph. D. Pins www2.austin.cc.tx.us/HongXiao/Boo k.htm 49 Heating and Bumps Melt Bumps Chip Socket Hong Xiao, Ph. D. Pins www2.austin.cc.tx.us/HongXiao/Boo k.htm 50 Flip Chip Packaging Chip Socket Hong Xiao, Ph. D. Pins www2.austin.cc.tx.us/HongXiao/Boo k.htm 51 Molding Cavity for Plastic Packaging Top Chase Bonding Wires Molding Cavity IC Chip Lead Frame Chip Bond Metallization Pins Bottom Chase Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 52 Ceramic Seal Bonding Wires Cap Seal Metallization IC Chip Ceramic Cap Layer 2 Layer 2 Lead Frame, Layer 1 Pins Chip Bond Metallization Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 53 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 Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Boo k.htm 54
