1. Introduction to semiconductor cleanroom
National nanofabrication centre
Indian Institute of Science
Bangalore

2. Outline Aim What is cleanroom? Why cleanroom training? Contamination
Cleanroom protocols
Do’s and don't's

3. Aim
Appreciation of cleanroom practice so that You keep it clean and Do reproducible research

4. What is a clean room? A clean room has a controlled environment
Low contamination (like dust, airborne microbes, chemical vapours etc)
specified by the number-of-particles/ft3 at a specified particle size
Eg: Room with < 100 particles/ft3 equal to or larger than 0.5 micron is a class 100 clean room.

5. Classification of cleanrooms
maximum particles/ft³
ISO equivalent
≥0.1 µm
≥0.2 µm
≥0.3 µm
≥0.5 µm
≥5 µm 1 35 7 3
ISO 3 10
350 75 30
ISO 4
100
750
300
ISO 5
1,000
ISO 6
10,000 70
ISO 7
100,000
700
ISO 8

6. Principles of the Clean Environment
Non-unidirectional
Unidirectional - Laminar
HEPA- high-efficiency particulate air filter
This has been likened to a "piston effect" where incoming clean air "pushes" contaminated air from the room.
The advantage of unidirectional flow is that airborne particles are carried out of the room in minimum time and the shortest path, thereby giving them less chance to start any trouble.
Laminar flow cleanrooms have generally parallel streamlines and approximately uniform velocity throughout.
They "clean" the air by transporting particles in the direction of the airflow out of the cleanroom.
Non-unidirectional rooms have non-parallel flow streams and non-uniform velocities. These rooms operate on the principle of the "dilution effect," with clean air entering the room and diluting the contaminated air.
This mechanism is similar to placing a garden hose into a bucket of muddy water and stirring the water while letting the excess drain out over the top. Eventually the clean water entering the bucket will dilute and displace the dirty water.
Non-un directional: The air flow system is the same as the common air-conditioning system except it uses a HEPA filter and more air changes to reduce the contamination level. This type of clean room is generally employed to maintain Class 1,000 to 10,000, but when it is supplemented by local laminar flow work stations, it can provide a high degree of contamination control for critical operations. The construction cost is economical.
"piston effect“- where incoming clean air "pushes" contaminated air from the room
"dilution effect“- non-parallel /non-uniform flow streams and velocities. clean air entering the room and diluting the contaminated air.

7. Why the training?
The Clean room environment is carefully maintained at particular standards and has equipments which are delicate and precisely calibrated
The chemicals and gases used in the facility may be extremely hazardous
Misuse may lead not only to destruction/malfunctioning of the device, but could also pose danger to personnel/instrument

8. Contamination types
• Molecular contaminants • Surface contaminants • Particulate contaminants
Contamination during process

9. Molecular contaminant sources
Out gassing
Oil vapours
Alcohols
Paints, glues, & epoxies
Aromatics; If you can smell it, suspect it as a contaminant

10. Sources of surface contamination
Finger prints - Oil & grease
Skin oil
Hand cream
Face cream, Wax
Polish

11. Sources of particulates
People (skin, scales, hair, clothing lint, etc.)
Particle shedding materials (cardboard boxes, paper)
Abrading actions (drilling, sawing, sanding, etc.)
Bare wood products

14. What you wanted What you got
Effect of Contamination Presence of a fibre on the mask during lithography
What you wanted What you got

15. Human hair on IC surface!
14/08/2013

16. High contamination source ?

17. Contamination Sources
People ~75%
Ventilation ~15%
Room Structure ~5%
Equipment ~5%

18. You are the Primary Contaminant!

20. Clean room Protocols
Rules and policies are no substitute for common sense.
Plan ahead. Get appropriate advice.
Do not start when in doubt.
Keep good house keeping habits.
DO NOT WORK ALONE or when stressed or NOT WELL
FOLLOW BUDDY SYSTEM, ESPECIALLY AFTER HOURS

21. Violation of Rules Depending on the gravity of violation
You may get just a warning
You may get your booking cancelled
You may loose your registration for a short while Or
You may loose your clean room registration all together!
REMEMBER, monitoring cameras are everywhere in the clean room!
Rules apply 24X7

22. Access Download the authorization form Fill, sign and submit it.
Read clean room protocols and safety documents.
Take the clean room test.
PASS IT, you are in!
Authority to enter does not mean
authority to operate instruments

23. Bookings Be there with your sample 15 min before your booking starts
No more than 2 bookings allowed per week
If you can’t make it to a booking, please inform in advance (1 day before)
If you book, but do not turn up, no slots for you for one month!
All processes have to be documented in the log book kept near the equipment/wet bench

24. In the clean room Use appropriate personal protection equipments (PPE)
In the wet bench area
In the main clean room

30. Q: Why is the procedure important?
Want the dust you generates to fall INSIDE your suit, NOT OUTSIDE.
So, the boot covers go OVER the suit, NOT UNDER
If you put on your gloves and then use your hands to gather your hair and put it under a cap, the gloves will have oil and skin flecks on the outsides from your hair. 

33. Protocols continued. Visitors allowed with permission only
Carry only things necessary for expt
No books, pencils allowed, ask for lint free paper for taking notes
Use pass-through for transfer of materials – no storage allowed

34. Protocols continued..
Permission needs to be obtained from the concerned authority before new material is brought into clean room
Access to the clean room does not automatically permit the use of equipments. Specific training and authorization is needed.
Talk to your supervisor and the concerned technologist if you need to be an authorized user.
If equipment is found faulty, do not try to repair, inform the concerned technologist and make a note in log book

35. Emergency Protocol (In Response To An Alarm)
Stop the process by pressing the emergency stop buttons of the equipments (if known)
Immediately alert the staff concerned (phone numbers are near the door) or call BMS : “115”
Evacuate the area by the nearest exit if ordered evacuation by the Building management system (announcement will be made)
Evacuate if power does not restore in 2 min
Do not wait to remove the gown for evacuation
Incase of a gas leak alarm, evacuate immediately

36. http://sindhu. ece. iisc. ernet
Entry protocol
Fire evacuation
Google – TWIKI iisc nnfc

37. Chemical Safety Training
To ensure a safe environment for learning and research
To prevent fatal Injuries and accidents
HF/BHF burns
Wet benches are the only safe places for chemicals

38. Wet Bench Protocol While working on wet bench, it is mandatory to
Wear lab shoes
Wear Aprons
Wear safety glasses/ face shield
Wear appropriate gloves
Make sure exhaust is functioning

39. Use of gloves PVC/LATEX NITRILLE TRIONIC (MAPA)
Chemie Opleiding
Use of gloves
PVC/LATEX
Are used protect wafers from particles generated by humans
No resistance to chemicals
NITRILLE
Thin chemical resistant gloves
Strong material : used for installation and maintenance of tools
TRIONIC (MAPA)
Thick chemical resistant gloves : used for cleaning up leaks
Nevertheless don’t put your hands in liquid chemicals!
The choice of gloves is dependent of the kind and the duration of the work that has to be executed with them and the kind of chemicals that have to be manipulated.
Certain tests are done to check the resistance to chemicals and the strength of the material.
Before use the gloves should be checked to see if there are any holes in them.
The reuse of gloves should be avoided. Only the thick Trionic (Mapa) gloves can be reused, but make sure they are not contaminated.
Other gloves should be thrown away inside out immediately after use so that the contamination stays at the inside.
Dienst Contaminatie Controle

40. Heavy Duty Neoprene
TRIONIC (MAPA
Chemical spill pillows
Chemical spill pads

41. Protocols
All chemicals in the fab are hazardous. Ensure that you have read the MSDS of the chemical before use
Never rub in your eyes or face with your hands or gloves.
AAA principle: Always Add Acid to Water
SOMEBODY WORKING AFTER YOU IN A LAB HAS TO TRUST EVERYTHING IS CLEAN!

42. Strictly, Chemicals should be used only in the fume hoods
All chemicals in the bay need to be labeled
Do not randomly mix chemicals since this may result in an explosion / evolution of hazardous gases
Appropriate face masks and gloves have to be worn before starting the expt. Please note that latex gloves used for clean room entry has no chemical resistance. Wear nitrile / acid resistant glove depending on your experiment.
Cool the chemicals before pouring them down the appropriate drain/bottle. If in doubt, ask the concerned person.
In case of chemical spill on floor, use the appropriate chemical blanket. When the spill is on person, remove contaminated clothing and get under safety shower. Flush eyes with copious amounts of flowing water for chemical spill is in the eye.

43. More..
Fluoride solutions to be used only in plastic beakers/petridishes/measuring cylinders
Fluoride etches glass!
Other acids to be used only in glass beakers
Transferring of Chemicals allowed only with full PPE
Solutions left for cooling/later use need to be indentified using identification chit
Please enter your process in the log book
No contact lenses please

44. What is an MSDS? What is an Material Safety Data Sheet
Tells what chemicals are in the product,
What the hazards of the chemicals are
How to protect yourself from the hazards.
Where to get M.S.D.S
Manufacturer websites, or
Google search “MSDS + name of chemical product” MUST READ !!
The label on the bottle also will contain some relevant information

45. Hazard Symbols

47. Disposal of Chemicals
Alkali’s and Acids can be poured down the drain after cooling!
HF and BHF solutions to be disposed in a single plastic bottle
Solvents in a separate bottle, separate bench provided, should not be poured down the drain
Do not leave anything on the wet bench uncleaned/unclaimed after use

48. Fluoride Solutions Hydrofluoric acid and Buffered HF solution
Equally hazardous
Highly dangerous due to the internal tissue and bone damage (Decalcification) caused by contact with the colour less liquid!

49. Symptoms HF injury: HF 49%
Almost immediate deep throbbing pain, burning feeling,(especially at hands and finger tips)
Red discoloration with whitish blister, tissue under skin starts dying off, bone de-mineralises
Systemic fluoride intoxication
Painful treatment in hospital (death possible)

50. Symptoms HF injury: Diluted HF solution < 20%
Sometimes it can take upto 24 hours before symptoms appear (pain, rash)
Might result in deeper penetration and more painful burn (especially at hands and finger tips )
The surface symptoms are minimal or may be absent
Can cause white discolored skin, blisters seldom form
HF solution >20%<49%:
Symptoms sometimes just noticeable after a few hours!
Treat all unlabelled, water-like solutions as HF solutions

51. First Aid Wash with large amounts of water (minimum 15min)
Rub in Calcium gluconate gel (make sure your hand is not contaminated) and cover the burn with plastic foil
Seek medical attention
Calcium Gluconate Gel is in the First aid box at the wet etch

52. Other Acids and Bases Strong acids used: Weak acid used Bases used
Sulfuric, Nitric, Hydrochloric, Phosphoric
Weak acid used
Acetic acid
Bases used
Potassium hydroxide, Sodium hydroxide, TMAH
The strong acids & bases are poisonous, corrosive, and will cause severe burns to body tissue. Long term exposure will cause lung and tooth damage. The weak acids will cause eye, skin and mucous membrane irritation and burns. Some are even carcinogenic or teratogenic.
READ THE MSDS
Wash thoroughly with water (safety-shower/eye wash) for 15 min and seek medical attention depending on the severity of the burn

53. Other commonly used
Hydrogen Peroxide: Colorless. Irritation and burns to skin and eyes.
Acetone, Isopropyl Alcohol (IPA) and Methanol:
All solvents may cause skin and eye irritation. They are colorless & combustible, should NEVER be heated for use. Solvent vapors are toxic, use only in ventilated hoods.

54. Photoresists
Photoresists are organic polymers which change their chemical structure when exposed to ultraviolet light.
Photoresists are harmful, carcinogenic and can be absorbed through unbroken skin.
They are generally flammable and should be kept away from any source of heat and ignition. Protective gear has to be used at all times when dealing with Photoresists
Compressed and liquefied gases
Chemical and Physical dangers
are caused by the properties of the gas inside and physical hazards due to the high power of a pressurized gas in a cylinder.
Gas leakages can also displace oxygen in the fab environment and lead to unconsciousness and ultimately death.

55. Cleanroom Don’t’s
Do not bring any tools/ equipment from outside into the cleanroom.
No bare clothes are allowed inside the cleanroom.
Do not expose any facial/head hair.
Do not open the door energency exits unnecessarily

56. Cleanroom Don’t’s
Do not open the door to the cleanroom for communication or passing of products back and forth – use the pass-through instead.
Do not use pass-through for storage.
Do not block the air flow from the filter to the product.
Do not congregate. No running and try to maintain silence

57. How to Become An Authorized User
Attend NNfC Orientation Course
Attend Weekly training
Take Cleanroom Protocol Test No
Pass
User is not authorized to enter cleanroom
Yes
User is authorized to enter cleanroom
Apply for approval for specific Equipment use
Reserve slots and use equipment

58. How to Become An Independent User
Apply for Training
Training by equipment owners
Certification by equipment owners
user clears the Test No
Yes
Becomes an independent user
Frequency of use > once/week
Yes No
Retraining and certification by equipment owners

59. User agreement All are expected to sign USER Agreement
before becoming authorised USER
Violations of Nanofab protocol and procedures
penalty points and restricted access and privileges

60. Penalty point chart Cumulative Disciplinary action penalty points
>30 points Loss of independent user status
for 2 weeks
>60 points 1 week suspension
>90 points 2 week suspension
>100 points Barred from access to the cleanroom.

61. M.N. Vijayaraghavan NNFC
14/08/2013
M.N. Vijayaraghavan NNFC

62. Thank you