Cleanroom Technology Farshid Karbassian
Outline • 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.
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.
Types of Contaminants • dust • bacteria • chemicals • electrical charges Whilst there are many different potential contaminants, these four pose the greatest threat:
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
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.
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.
Y= 2/6=33.3% Y= 28/32=87.5% 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%!
Cleanroom History • Cleanroom is an environment that has much lower particle counts than normal environments. • Cleanrooms were historically usedin operating rooms to preventpost surgery infection.
Cleanrooms • 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.
Killer Particles • 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. Smaller feature size cleanroom with higher grade of purity
How to solve it? • HEPA Filter • Cleanroom furniture • Garments • Tight cleanroom protocols
HEPA 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.
Cleanrooms Classification • A cleanroom is identified by a class number which shows how cleanit is. • Standard definitions of cleanroom classification are a combination of metric and English units.
Cleanrooms Classification • A class 10 cleanroom has fewer than 10 particles with diameter larger than 0.5 µm per cubic foot.
Cleanrooms Classification • 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 Classification • 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 Structures Conventionally Ventilated Type of Cleanroom Unidirectional Flow Type
Particle Counter • Particle counter is used to count and size of the particles.
The Human Element • 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.
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.
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
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 Cotton Fabric Polyester Cleanroom Fabric
Bunny Suit • Shoe Cover • Cap • Face Mask • Safety Glasses • Hood • Coverall • Boots • Gloves
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.
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 length sleeves with fully adjustable wrist studs to overcome that tricky gap between sleeve end and glove. Suitable for wearers in 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.
Hood, Coverall, Boots Hoods 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.
front Coveralls back Rolled seams set-in sleeve coverall
Stud cuff Popular variations Coveralls 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. Knitted cuff Pocket Pen holder
Labcoats Features: 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 seams Collar: 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
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
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
Cleanroom Laundry • Micronclean has the expertise to manufacture specialist styles of garments and machine covers.
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.
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.
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.