clean room - Indian Institute of Science Bangalore

Introduction to semiconductor
cleanroom
National nanofabrication centre
Indian Institute of Science
Bangalore
Outline
•
•
•
•
•
•
Aim
What is cleanroom?
Why cleanroom training?
Contamination
Cleanroom protocols
Do’s and don't's
2
Aim
Appreciation of cleanroom practice so that
You keep it clean
and
Do reproducible research SAFELY
3
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.
Classification of cleanrooms
maximum particles/ft³
ISO
equivale
nt
Class
≥0.1 µm
≥0.2 µm
≥0.3 µm
≥0.5 µm
≥5 µm
1
35
7
3
1
ISO 3
10
350
75
30
10
ISO 4
750
300
100
ISO 5
100
1,000
1,000
7
ISO 6
10,000
10,000
70
ISO 7
100,000
100,000
700
ISO 8
Principles of the Clean Environment
Non-unidirectional
Unidirectional - Laminar
HEPA- highefficiency
particulate air
filter
"dilution effect“- non-parallel /nonuniform flow streams and velocities.
clean air entering the room and
diluting the contaminated air.
"piston effect“- where incoming clean
air "pushes" contaminated air from
the room
6
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
Contamination types
• Molecular contaminants
• Surface contaminants
• Particulate contaminants
8
Molecular contaminant sources
•
•
•
•
•
Out gassing
Oil vapours
Alcohols
Paints, glues, & epoxies
Aromatics; If you can smell it, suspect it as
a contaminant
9
Sources of surface contamination
•
•
•
•
•
Finger prints - Oil & grease
Skin oil
Hand cream
Face cream, Wax
Polish
10
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
11
Effect of Contamination
Presence of a fibre on the mask during
lithography
What you wanted
What you got
High contamination source ?
Contamination Sources
•
•
•
•
People ~75%
Ventilation ~15%
Room Structure ~5%
Equipment ~5%
You are the Primary Contaminant!
Personal Protection equipments
• Use appropriate personal protection
equipments (PPE)
– In the wet bench area
– In the main clean room
Gowning Protocol at NNFC
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.
Just after you enter
• A class 100 area at the entry point
• Make sure the door is open from one side
• Make sure you spend a minute there
Clean room Protocols
• Rules and policies are no substitute for common
sense. Please note that strict action will be taken
against those violating the rules
• 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.
• Cleanroom hours: 6 am to 12 midnight, all 7 days of a
week
• Please contact any of the management representatives
if you have suggestions or feedback
Cleanroom protocols
• Please wash your hands and face with lots of
water before coming into the clean room
• If you ate something just before coming into
the cleanroom, drink water and rinse your
mouth thoroughly
• If you smoke, drink water before coming into
the cleanroom
• Do not come in with torn and/or dirty socks
Cleanroom entry
Allowed:
• Clean, dry clothes are mandatory.
• Half/full sleeved shirts (shirts should cover from arms
to waist) and full length pants (covering from waist to
ankles) are required.
• Churidhars and Salwars are allowed.
• Clean socks or stockings are mandatory.
Note: Please make sure that long or medium length hair
is tied back. Contact lenses are strictly prohibited
During Pregnancy
• Please avoid using the cleanroom during
pregnancy and breast feeding
– Be a dependent user for the duration
• In case cleanroom entry is necessary, please
discuss the risks with the safety committee
members after submitting a copy of your
process details
• Retraining is necessary once your comeback
Cleanroom Entry: Not allowed
• Clothes which are dusty, dirty or wet
• Sleeveless clothes, shorts or short-pants
• Tank tops, halter tops and spaghetti strap tops,
sarees, skirts and gowns
• Clothes which shred fiber like fur, mohair etc
• Deodorants, perfumes and cosmetics including hand
cream
• Heavy jewellery and decorative accessories including
flowers
• People suffering from cough, cold or respiratory
diseases
• People with pacemakers
• Food and Beverages
Cleanroom entry
• Visitors allowed with
permission only
– Also make sure no one
enters with you
• 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
Cleanroom Don’t’s
• Do not bring any tools/ equipment from
outside into the cleanroom and do not take
anything away from the cleanroom.
• No using cellphones during processes
even if connected to hands-free.
• Do not expose any facial/head hair.
• Do not open the door emergency exits
unnecessarily
30
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 congregate. No running and try to
maintain silence
31
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
Equipment usage
• Two type of users: Dependent/ Independent
• Dependent authorized users: Only day time access /
process done by facility technologist, please book the
slot well in advance
• Independent users: Anytime access, after proper
training
• Talk to your supervisor and the concerned
technologist if you need to be an independent user.
• Internet usage (including FOM) on equipment
computers strictly prohibited. Use of pendrives is
also not allowed, use winSCP to transfer data
• Only chemicals in the cleanroom chemical list
allowed
Attend
Weekly
training
Attend NNfC
Orientation
Course
Repeated 3
times only
Take Cleanroom
Protocol Test
Pa
ss
No
Yes
User is authorized
to enter cleanroom
Apply for approval for
specific Equipment use
using FOM software
Reserve slots and
use equipment as
dependent user
User is not authorized
to enter cleanroom
Users not passing the test even
after 3 attempts should send
an email to Dr. Prabhakara Rao
and the decision will be taken
by the clean room committee
Dependent users are
temporary users (those who
will not use the tool more than
3 times)
Apply for
Training
Training by
equipment owners
Certification by
equipment owners
No
User clears the Test
and uses the tool
specified no. of times
without incident
Yes
Becomes an
independent user
Tool not
used for
3
months
Retraining and
certification by
equipment owners
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
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
Penalty point chart (representative)
Cumulative
Disciplinary action
penalty points
>30 points
One week suspension
>60 points
Two week suspension full
cleanroom
>90 points
3 week suspension, no
cleanroom access
>100 points
Barred from access to the
cleanroom, case to go to
Cleanroom committee
Slot Bookings
• Slots need to booked using FOM software before tool
usage.
• Be there with your sample 15 min before your booking
starts, 30 minutes before a litho slot
– Samples submitted 15 min after the beginning of the slot
will not be accepted
• Restrictions on no. of bookings per week depending on
the tool
• If you can’t make it to a booking, cancel as soon as you
can
• If you book, but do not turn up, penalty points as per
norms
– Also, the slot will be charged
• All processes have to be documented in the log book
kept near the equipment/wet bench
Slot cancellation on FOM
• Slots booked on FOM will not be honored if
– Slots booked by dependent users using express
logon
– Slots booked by dependent users after official
hours
– Slots booked without relevant information
• Process conditions
• Materials information (different layers, pre process)
– Slots booked by users who are under suspension
from the cleanroom
In case of tool break down
• Inform the concerned facility technologist (phone
numbers available on the twiki page)
– Call from outside the fab incase of network problem
• Send ‘Instrument problem report’ to the
instrument managers using FOM
– Log off and press the “something wrong” button
• If unable to contact FT’s, please put the tool
down notice and send an email to the FT and
technology manager
• DO NOT TRY TO REPAIR BY YOURSELF
Communications from the Cleanroom
• FOM sends a notice to all users
– Make sure your registration email is your official
IISc email id
– Notices cannot be send to other gmail, yahoomail
etc
• General email to all CENSE users
• Broadcast emails send to IISC
• Notice on NNFC twiki, FOM “users note”
Materials restrictions
• Sulfur
• Fast diffusing and toxic metals like Fe, Cu, Cd, Mn,
Zn, Sb, Se, As and Hg and their alloys
• PDMS (PV lab)
• Only chemicals mentioned in the Chemical list of
twiki is allowed at the wet bench
• Only Photoresists mentioned as standards for
each lithography tool is allowed at the litho bay
New Materials Entry
(chemicals/photoreists/wafers/targets etc)
• Permission needs to be obtained from the
concerned authority before new material is
brought into clean room (procedure in twiki)
– Send detailed mail to Dr. Savitha containing the
following details
•
•
•
•
Prior process
Post process
MSDS of the material
Why the cleanroom need to be used
Emergency: Call
115
• 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
Alarm Response
• Common Alarms: Fire and Smoke
– In the cleanroom corridor, outside Films room
– Inform BMS at 115 and wait for instructions
– If asked to evacuate, do it by the nearest exit
• Gas alarms
– Specific to equipments, mainly LPCVD, Diffusion furnace
and PECVD
–Alert nearby users and evacuate
immediately through emergency
exit
– Inform BMS by calling 115 from the cleanroom outside
corridor phones
http://sindhu.ece.iisc.ernet.in/nanofab/twikii/bin/view/Main/WebHome
Google – TWIKI iisc nnfc
Entry
protocol
Fire
evacuation
Contamination Policy – Different
Levels
LEVELS
Materials Allowed
LEVEL 0 (Colour code: Dark blue)
New full prime wafers only
LEVEL 1 (Colour code: Light blue)
Unprocessed wafers, wafers coming after
an RCA clean on Level 2 wet bench,
Metals not allowed
Wafers processed in LEVEL 2/1/0
equipments, from Litho without metal
contamination, Metals not allowed
LEVEL 2 (Colour code: Green)
LEVEL 3 (Colour code: Orange)
Metals allowed
LEVEL4 (colour code: Red)
Metals allowed, final processing step, not
allowed entry into another tool after this
step
LEVELS Bay-wise: Wet etch
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•
•
•
•
•
•
•
WB 1, Precleaning bench: Level 0
WB2, CMOS non metal: Level 1
WB3, Metal etch (electroplating): Level 3
WB4, Solvent bench: Level 2/Level 3
WB5, MEMS bench: Level 3
General wet bench: Level 1
Electroplating bench (General wet bench): Level 2
HF vaporiser: Level 3
• Glassware to be quartz or low alkali borosil, glassware
exchange strictly prohibited
Diffusion bay
• First Nano oxidation and Doping furnaces: LEVEL 1
Only Si substrates from LEVEL 1 wet bench
• First Nano metal annealing furnace: LEVEL 2 Semiclean
Only metals Al, Ti and W allowed
• First Nano drive-in/dielectric annealing furnace: LEVEL 1
• LPCVD furnace (Except tube 2): LEVEL 2
• LPCVD furnace (Tube 2): LEVEL 4
• RTP 1 (4 inch): LEVEL 4
• RTP 2 (6 inch): LEVEL 1
Only Si substrates from Level 1 wet bench
Lithography (Level 3)
• All type of clean room compatible samples allowed.
• Metals lift-off needs to be done only on the solvent
bench at wet etch (WB4)
Attempt to restrict wet processing of metal contaminated
sample to one bench
• All SU8 processing strictly confined to SU8 bench (with
own set of glassware)
• Only Approved resists on Spin coaters
Dry Etch
• Oxford PECVD system: LEVEL 2/3
Level 2 processing allowed with a prior Chamber
clean
• Oxford RIE Cl system: LEVEL 3
• Oxford RIE F system: LEVEL 2
• SPTS DRIE system: LEVEL 2
• ALD system: Level 3
Films
• Tecport metal sputtering unit: LEVEL 3
• Tecport dielectric sputtering unit: LEVEL 2
• Tecport evaporation unit: LEVEL 3
Equipment Development/Inline
Characterization room
• Tempress metal annealing furnace: LEVEL 4
• Tempress dielectric annealing: LEVEL 4
• Inline characterization equipments: LEVEL 3
Samples from non-cleanroom
environment
• Non-cleanroom environment:
– PV lab, Polymer processing, other labs
– Allowed only on
• lithography equipment (if not a heavy contamination
threat)
• inline characterization bay and
• Level 4 furnaces
Sample flow during diffusion (full
wafer)
Level 0 WB
RCA
Furnace
Level 2 RCA
Level 1 RCA
Lithography
Clean chuck
Diffusion
furnace
Level 2 WB
oxide etch/
resist strip
Level 1
psg/bsg etch
Responsibility of the user
• Proper and professional conduct
• Not cause disturbance or disrupt the
procedures of other users
• Report any violation noticed immediately to
the Nanofab staff
• It is the responsibility and need of each user
that the fab is maintained at the optimum
levels
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
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
Gowning protocol for Hydrofluoric acid
Use of gloves
 PVC
– 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!
F-telon gloves (Teflon incorporated)
Chemical spill pads
TRIONIC (MAPA
Chemical spill pillows
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.
• Never touch the phone or the taps wearing
contaminated gloves
• AAA principle: Always Add Acid to Water
SOMEBODY WORKING AFTER YOU IN A LAB HAS TO TRUST EVERYTHING IS CLEAN!
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
Hazard Symbols
Strictly,
• Chemicals should be used only in the fume hoods
• All chemicals in the bay need to be labeled
– Solutions left for cooling/later use need to be indentified
using identification chit
• Do not randomly mix chemicals since this may result
in an explosion / evolution of hazardous gases
• Appropriate face masks/ goggles 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.
Use of glassware
• Fluoride solutions to be used only in plastic
beakers/petridishes/measuring cylinders
– Fluoride etches glass!
• Other acids to be used only in glass beakers
• Exchange of glassware between benches strictly
not allowed
– Glassware is labeled and belongs to particular benches
• Transferring of Chemicals allowed only with full
PPE
• Please enter your process in the log book
• No contact lenses please
Disposal of Chemicals
• Alkali’s and Acids can be poured down the drain after
cooling (<50 deg C)!
• Chrome etch to be disposed into single plastic bottle
• 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
• Si wafer/glass pieces to be discarded in the designated bin
at the wet etch
• On person
Chemical spill
– Remove contaminated clothing and get under safety
shower
– Seek medical attention
– Inform BMS
• On the floor
– Small
• Dilute with water and put spill blankets, discard spill blankets
in the plastic dustbin
– Big
• Come out and close the door to the wet etch
• Inform BMS immediately
• Take precautions not to breathe in the fumes
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!
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 demineralises
• Systemic fluoride intoxication
• Painful treatment in hospital (death possible)
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
First Aid
• Wash with large amounts of water (minimum
5min)
• 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
Most of the harm from HF exposure can be minimized if
washed within minutes
•
•
•
•
Other
Acids
and
Bases
Strong acids used:
– Sulfuric, Nitric, Hydrochloric, Phosphoric
Weak acid used
– Acetic acid
Bases used
– Potassium 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.
– TMAH and KOH causes severe eye damage and blindness
– Exposure to 25% TMAH might cause respiratory failure
• First aid: Wash thoroughly with water (safetyshower/eye wash) for 15 min and seek medical
attention depending on the severity of the burn
Eye Shower
Safety Shower
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.
Photoresists
• Photoresists are organic polymers which
change their chemical structure when exposed
to ultraviolet light.
– They are generally flammable and should be kept
away from any source of heat and ignition.
– Could be carcinogenic / irritant/ harmful / cause
depression of central nervous system and damage
to liver and kidneys
– Protective gear has to be used at all times when
dealing with Photoresists
Photoresist Developers
• Mostly use TMAH (Tetra methyl ammonium
hydroxide)
– Severe eye damage might effect from exposure to
TMAH
– Could cause chemical burns on skin contact
– Dermal exposure might also cause respiratory
failure/ cardiac arrest
On skin contact , wash with large amounts of water
(minimum 15 minutes) and contact BMS. PPE’s
mandatory at developing stations
Penalty points at the wet benches
(nx times for second violation)
• Using without booking slots: 15 points
• Not wearing proper PPE (gloves/ goggles): 15
points
• Exchanging glassware: 15 points
• Leaving solutions without identification chit: 15
points
• Leaving bench unclean: 30 points
• Using BHF/HF/ Vaporizer carelessly: 100 points
(immediate suspension of cleanroom access)
• Bringing external chemicals without permission
(across all the bays): 100 points
Minor Spill Criteria
Chemical
spill
On bench/
floor
On person
Minor spill
Remove clothing
and get under
safety shower
Dilute with water
and absorb the spill
using chemical spill
blankets/ pillows
Inform BMS
immediately at 115
Dispose the spill
blankets in the
plastic dustbin
 Not in immediate danger
of an explosion, fire or a
health issue
 Not spreading further (is
only on small area (<2x2 ft)
and is not HF
 Dangerous only by direct
contact
Can be managed by
existing PPE
Major spill
Try not to breathe
the fumes
Evacuate and put
red tape across the
door preventing
user entry
Call BMS
immediat
ely at 115
HF exposure
Wash with large amounts of
water (min 5 min)
Apply calcium gluconate gel
using uncontaminated gloves
Call BMS immediately at 115
Continue applying
Calcium gluconate
gel till your get to the
doctor
14/08/2013
M.N. Vijayaraghavan NNFC
83
Entry
MJB3
Mask
aligner
EVG
Bonder
Safety
Shower
WB1 WB2
WB5
In line Char
E-Beam evaporator
FTP
WB4
Wet Etch room
EP Bench
Micro
scope
Old
CMOS
bench
New Wet Old Wet
bench
bench
N2
Emergency
Rescue
and EHS
Officer
C
l
e
a
n
r
o
o
m
N1
Control
room
C Films
WB3
E-Litho 1
Laser
Writer
Four point
probe
Sputtering Units
C
l
e
a
n
r
o
o
m
EVG
Aligner
Laundry
Dektak
Ellipsometer
Air
shower
Gowning
First Aid box
Oven
EYE WASH
Dry Cleanroom
Etch
Room
Cleanroom
inner
corridor
inner
corridor
C
o
r
r
i
d
o
r
C
o
r
r
i
d
o
r
F Litho 2
New Wet
Bench
SU8
Developer
Oven
Diffusion
DRIE
RIE- F
Sintering and
Annealing
G Litho 3
RIE-Cl
Raith ELine
Chiller
control
Raith
Pioneer
ALD
PECVD
5 target
sputter
tool
Oxidation and
Doping
LPCVD
Ar ion
milling
GaN
Reactor
Equipment Development
Multi
target
sputter
and PLD
tool
Tempress
Dry/Wet
Oxidation
CPD
Savitha P, NNFC
84
Thank you