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Standard Operating Procedure
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Read the EH&S Standard Operating Procedures Fact Sheet before filling out this form.
Print out the completed SOP and keep a readily accessible hard copy in the lab (also
keeping an electronic copy is highly recommended).
______________________________________________________
Date:
SOP Title:
Using Piranha Solution for cleaning
Principal Investigator:
Room and Building:
Lab Phone Number:
Section 1 – Process
A piranha is used to remove organic residues from substrates. Two different solutions are used. The
most common is the acid piranha: a 3:1 mixture of concentrated sulfuric acid (H2SO4) with 30%
hydrogen peroxide (H2O2).
Section 2 – Hazardous Chemicals
sulfuric acid (H2SO4) and 30% hydrogen peroxide (H2O2)
Section 3 – Potential Hazards
HIGHLY CORROSIVE
STRONG OXIDIZER - May ignite flammable/combustible materials: DO NOT mix with ORGANIC
solvents
OVERPRESSURE EXPLOSION HAZARD – DO NOT confine while reaction continues to out-gas
INHALATION HAZARD – perform work inside a fume hood
Section 4 – Approvals Required
Use of piranha must be approved by the Principal Investigator or Lab Safety Officer
Section 5 – Designated Area
Inside chemical fume hood
Section 6 – Special Handling Procedures and Storage
Requirements
Whenever handling Piranha, only use glass containers (preferably Pyrex). Containers used during the
experiment must be very clearly labeled and a warning sign, visible by any user working inside the
fume hood, must be posted at all time to indicate that the solutions contains Piranha mixture.
Mix the solution in the fume hood with the sash between you and the solution. Wear full personal
protection, as described in Section 7.
When preparing the piranha solution, always add the peroxide to the acid. The H2O2 is added
immediately before the etching process because it immediately produces an exothermic reaction with
gas (pressure) release. If the H2O2 concentration is at 50% or greater, an explosion could occur. Start
out making small quantities, until you work out how much you need.
Piranha solution is very energetic and potentially explosive. It is very likely to become hot, more than
100 degrees C. Handle with care.
Substrate should be rinsed and dried before placing them in a piranha bath. Piranhas are used to
remove photoresist and acetone residue, not the compounds themselves
Leave the hot piranha solution in an open container until cool.
Never store hot piranha solutions. Piranha stored in a closed container will build up pressure and
possibly explode, spraying concentrated acid.
Adding any acids or bases to piranha or spraying it with water will accelerate the reaction. This
includes Photoresist, which is a strong base.
Mixing hot piranha with organic compounds may cause an explosion. This includes acetone,
photoresist, isopropyl alcohol, and nylon.
Do not store wash bottles containing organic compounds on the piranha deck.
Section 7 – Personal Protective Equipment
The handling of Piranha solutions requires special protection equipment in addition to the regular
clean room protection outfit
The additional protective equipment include: a full face shield, heavy duty rubber gloves (disposable
Nitrile gloves will not provide sufficient protection), as well as an acid apron to wear on top of the lab
coat.
Heavy Gloves are located in the cabinet, apron and face shield are available at ____________.
As a reminder, open-toed shoes are not allowed when working in the lab and legs must be covered
Section 8 – Engineering/Ventilation Controls
Always work within a fume hood. Use sash to protect yourself from an accidental spraying of piranha.
Make sure emergency eyewash is accessible and working properly before working with such
hazardous materials.
Section 9 – Spill and Accident Procedures
In case of large exposure, the victim should be removed from the contaminated area, decontaminated
under a safety shower while emergency personal is contacted (911).
All contaminated clothing should be removed immediately with appropriate gloves and safely
discarded.
In case of contact with the skin, the affected area must be immediately rinsed with large amounts of
water for at least 15 min.
In case of contact with the eye, irrigate the eye for at least 30 minutes, keeping the eyelids apart and
away from eyeballs during irrigation. Call 911, Place ice pack on eyes until reaching emergency room.
In case of inhalation, it may irritate the respiratory tract. Conscious persons should be assisted to an
area with fresh, uncontaminated air. Seek medical attention in the event of respiratory irritation,
cough, or tightness in the chest. Symptoms may be delayed.
Section 10 – Waste Disposal
The primary hazard from storage of piranha etch waste is the potential for gas generation and over
pressurization of the container when the solution is still hot. If you store a hot solution in a tight
container, it will explode!
Therefore prior to storing the piranha solution, it must be left in an open container in order to cool
down for several hours (overnight). It is your responsibility to make sure that the open container is
very clearly labeled and left in a safe area for overnight cool down.
Once cooled down, the solution can be transferred into a loosely-capped glass container for waste
storage. The container must be very clearly labeled with the solution name and composition and must
include VERY VISIBLE warning signs not to add any other types of chemicals. Keep waste bottles
loosely caped or use a vented cap. Verify there is no pressure before picked up for disposal through
EH&S.
Section 11 - Decontamination
Rinse contaminated beakers and glassware with lots of water. Carefully pour the piranha solution into
the piranha waste beaker in the piranha hood.
Section 12 – Process Steps
Process Steps
1. Place chips on glass slide (~ 4 chips for
40mL)
Safety Measures
Put on personal protective equipment, section 7
above. Make sure eyewash is working.
2. In hood, pour 30mL H2SO4 in beaker.
3. Add 10mL H2O2 & swirl gently.
4. Take levers on slide in one hand, & using
tweezers in other hand to lower levers into
beaker (watch orientation – don’t smash
levers on bottom) & tap tweezers between
levers.
5. Let sit ~30min (room temp). Put sign up
on hood.
6. Rinse tweezers in lots of water.
7. Rinse & dispose of slide.
8. Tighten H2SO4 cap, rinse bottle, dry, &
put away.
9. Fill 2 1000mL beakers with ~800mL DI
water and one 100mL beaker with
~100mL DI water. Pickup chip (make
sure you have a good grip!) & swirl gently
for ~15 seconds in each of the large
beakers. Then place in smaller beaker.
Exothermic reaction – hot!
10. Repeat step 9 for all chips.
11. Dry on cleaned slide. Tap gently (non
lever side!) to remove water and then
leave under scope with light on.
12. Check levers to see if chip is usable (all
there? Cracked?). Store in dessicator.
13. Clean up: Clear out sink. Rinse the “rinse
beakers” with lots of water. Carefully
pour the piranha solution into the piranha
waste beaker in the piranha hood.
DO NOT tighten the cap!
Training Documentation
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