Cleanroom Technology

Farshid Karbassian

Outline

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• Contaminants• Yield• Historical Overview• Killer Particles• Cleanroom Classification • Cleanroom Structure• Garments• Cleanroom Protocols

Contamination

• Contamination can be considered as anything which has an effect on the quality or performance of something being created.

• Contaminates can take the form of particulate, biopollutants, chemical cross-contamination or electrical charges, which individually or collectively can have a deleterious effect on product or process performance. 3

Contamination Control

• Contamination control is a key element in the concept of the zero defect philosophy.

• By working within a controlled area like a cleanroom, some pollutants can be filtered out, others eliminated by improvements in the production environment.

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Types of Contaminants

• dust• bacteria• chemicals• electrical charges

Whilst there are many different potential contaminants, these four pose the greatest threat:

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Yield

• Yield determines weather a fab is making profit or losing money.

• It depends on many factors, including people, environment, materials, equipment, and processes.

• Wafer yield, die yield, and packaging yield

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Wafer Yield

• Wafer yield depends on processing and wafer handling.

• Careless human handling and robot malfunction or miscalibration can break the brittle wafers.

• Faulty processes e.g. wrong dopant concentration, poor uniformity, or large amount of particles on wafers can also ruin wafers.

total

good

W Wafers

WafersY =

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Die & Packaging Yields

• Die yield is related to factors such as particle contamination, process maintenance, and total process steps.

• Packaging yield relates to the wire bonding quality and specification difference between the die test and the chip final test.

• The overall yield is the product of all three equations.

total

good

C Chips

ChipsY =

total

good

D Dies

DiesY =

CDWT YYYY ××=

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Yield

• More than 300 steps to build an IC.• The die yield of 99% at each process

step will lead to overall yield of 4.9%! Killer defects

Y= 28/32=87.5%Y= 2/6=33.3%steps process ofnumber :n

area chip:A

densitydefet killer :D

)DA1(

1∝Y n+

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Cleanroom HistoryCleanroom History

• Cleanroom is an environment that has much lower particle counts than normal environments.

• Cleanrooms were

historically used in operating rooms to prevent post surgery infection.

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CleanroomsCleanrooms

• Microelectronics and the pharmaceutical industries started using cleanrooms in the 60’s and 70’s.

• Since the 80’s other industries e.g. optical, biotechnology, telecommunications, aerospace & defense, medical devices, cosmetics, and food processing industries became interested in the advantages of cleanrooms for their critical production processes.

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Killer ParticlesKiller Particles

Smaller feature size cleanroom with higher grade of purity

• Just one more particle count on each wafer could cost a 4” wafer fab more than $1.3 million a year (1980s)!

• When feature size shrinks, so does the size of killer particles.

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How to solve it?How to solve it?

• HEPA Filter• Cleanroom furniture• Garments• Tight cleanroom protocols

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HEPA FilterHEPA Filter

• The idea of the HEPA (high efficiency particulate air) filter was introduced in late World War ll, after it was found that some of the problems during

the assembly of the first atomic weapons were related to dust.

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Cleanrooms ClassificationCleanrooms Classification

• A cleanroom is identified by a class number which shows how clean it is.• Standard definitions of cleanroom classification are a combination of metric and

English units.

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• A class 10 cleanroom has fewer than 10 particles with diameter larger than 0.5 µm per cubic foot.

Cleanrooms ClassificationCleanrooms Classification

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• There are more than 500’000 particles with diameter larger than 0.5 µm per cubic foot inside a reasonably clean house.

• Cleanrooms of classes 100’000, 10’000, 1000, 100, 10, 1 in English scale have been used.

Cleanrooms ClassificationCleanrooms Classification

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• A fab making IC chips with a minimum feature sizes smaller than 0.25 µm needs a class 1 cleanroom to achieve an acceptable yield.

• The highest class of cleanroom, M-1, has fewer than 1 particle per cubic meter.

Cleanrooms ClassificationCleanrooms Classification

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Cleanrooms ClassificationCleanrooms Classification

Particle/ft3

Class 0.1 m 0.2 m 0.3 m 0.5 m 5 m

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

1’000 1000 7

10’000 10000 7019

Cleanrooms StructuresCleanrooms Structures

Equipment AreaClass 1000

Equipment AreaClass 1000

Process tool

Process tool

Fans

Raised Floor with Grid Panels

HEPA Filter

Return Air

Pump, Power Supply

Makeup Air Makeup Air

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Cleanrooms StructuresCleanrooms Structures

Conventionally Ventilated Type of

Cleanroom

Unidirectional Flow Type

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OUTSIDE CORRIDOR 0 Pa

20 Pa

0 P

a

PRODUCTION ROOM

MATERIALS TRANSFER ROOM

CHANGE ROOM

LOCKER ROOM

15 Pa

25 Pa

35 Pa

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Particle Counter

• Particle counter is used to count and size of the particles.

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• Between 40 % and 80 % of contamination can be traced to human operatives working in cleanrooms.

• Sex, age, temperature differentials and patterns of activity all have a bearing on the rate of issue, as do contaminants from clothing, cosmetics and personal hygiene.

The Human ElementThe Human Element

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Cleanroom Garment

• Since people are the greatest contaminants in a controlled environment, specialized garments are needed to protect the environment from the human contaminant.

• Cleanroom garments must meet specific protection criteria. This involves special materials, particular construction and individual styling.

• They must be comfortable, easy to apply and practical in use.

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Cleanroom Garment

The fabrics must:• be low shedding• permit the body to breathe whilst trapping

particles within the garment• withstand repeated cleaning/sterilization

cycles• meet any specific requirements like control

of static charges• be cost-effective

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Cleanroom Garment

• There are three broad categories of fabric used in the construction of cleanroom garments.

• woven fabrics• laminated or membrane fabrics• disposable or limited life materials

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Polyester Cleanroom FabricCotton Fabric

Bunny Suit

• Shoe Cover • Cap• Face Mask• Safety Glasses • Hood• Coverall• Boots• Gloves

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Bunny Suit

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Bunny Suit

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Gowning Procedure

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Undersuits

• Unisex tunic and separate trousers with moisture control system to maximize comfort. Tunics are either short or long-sleeved with security pocket for locker key. Trousers are pull-on with elasticated waist and adjustable ankle studs.

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Hat, Coat, Shoes

Hats are one size to fit all with toggled elastic adjustor to cover the most abundant hairstyles. Suitable for wearers in ISO 6 to ISO 8 cleanroom suites.

Coats come in a range of 8 sizes from XSM to XXXXL with a unisex fit, good zip flies to ensure minimal particle outage and longer lengthsleeves with fully adjustable wrist studs to overcome that tricky gap between sleeve end and glove. Suitable for wearersin ISO 6 to ISO 8 cleanroom suites.

Shoes have shaped soles with elasticated ankle grips offering comfort to the wearer. Sizes XSM to XXXL. Suitable for wearers in ISO 6 to ISO 8 cleanroom suites.

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Hood, Coverall, BootsHoods are made in one size to fit all with fully adjustable studding at the rear, long cowls to ensure the hoods do not untuck from body garments and overall hair and forehead cover. Suitable for wearers in ISO 4 to ISO 7 cleanroom suites.

Coveralls come in a range of 8 sizes from XSM to XXXXL with a unisex fit, good zip flies to ensure minimal particle outage and longer length sleeves with fully adjustable wrist studs to overcome that tricky gap between sleeve end and glove. Suitable for wearers in ISO 4 to ISO 7 cleanroom suites.

Overboots have shaped soles offering comfort to the wearer and fully adjustable tops and toe tapes. Sizes XSM to XXXL. Suitable for wearers in ISO 4 to ISO 7 cleanroom suites.

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Coveralls

front

backRolled seams set-in sleeve coverall

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Coveralls

Stud cuffKnitted cuff

Pen holder

Pocket

Popular variations

Features:Seam: Rolled seams, heat-sealed raw

edges. monofilament thread Sleeve: Set-in, 1 piece Cuff wrist: Stainless steel stud

adjustment, 3 male 1 female Cuff ankle: Stainless steel stud

adjustment, 3 male 1 female Collar: Cleanroom style collar, 2 male 1

female stud adjustment at top of zip Closure:       Fly front - closed end 70cm

polyester zip, nylon spiral teeth, opposite fastenings for male and female versions

Size range: Male - chest 88-146cm

Female - chest 76-104cm. 37

LabcoatsFeatures:Seam: Twin-needled, heat-sealed raw

edges, monofilament thread Sleeve: Set-in, 1 piece Cuff wrist: Polyester knitted cuffs Front: Centre front zip, open flap at

bottom, shoulder and side seamsCollar: Mandarin, 1 piece, top stitched at

the base Closure: 83cm open-ended zip, polyester

tape with nylon spiral teeth. Stainless steel studs at top, 2 male and 1 female.

Size range: Unisex XS-XXXL

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Headwears

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Footwears

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Cleanroom Laundry

• Micronclean’s ISO 4 cleanroom garment processing suite offers the latest in bespoke washers, dryers and packaging machines to ensure all your requirements are fully satisfied. All garments are processed using reverse osmosis water with a topical anti-stat applied preventing static build-up.

www.micronclean-newbury.co.uk

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Cleanroom Laundry

• Micronclean’s ISO 7 cleanroom garment processing suite offers an alternative service for cleanroom operators in lower grade cleanrooms and those requiring a high care workwear service.

www.micronclean-newbury.co.uk

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Cleanroom Laundry

• Micronclean has the expertise to manufacture specialist styles of garments and machine covers.

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Cleanroom Protocols

• People need to walk steadily, running or jumping could disturb particles on the floor, walls, and ceiling.

• Sitting on tables or leaning against walls is forbidden.

• There are few chairs in cleanrooms. • Bringing pencils and erasers to

cleanroom is forbidden.

Keeping particles from becoming airborne is the main goal.44

Cleanroom Protocols

• Specially made papers are used in cleanrooms. For a better than class 1, all records are kept electronically.

• Once one’s glove touches any skin it should replaced immediately.

• Technicians should leave the process area before sneezing or coughing.

Keeping particles from becoming airborne is the main goal.45

Cleanroom Protocols

• People who work in cleanrooms are not allowed to use cosmetics, perfume, cologne, or aftershave.

• Technicians cannot wear contact lenses.

• Smokers who want to work in cleanrooms are forced to quit smoking.

Keeping particles from becoming airborne is the main goal.46

Cleanroom Protocols

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Wipes

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Any questions?