Introduction: |
The acid hood is a general purpose chemical
hood which is used for the processing of small amounts of acids/bases
only. These chemicals
should be aspirated into the water drain after use. The acid-hood station
supports several processes, including etching, and "piranha"
cleaning of wafers. The materials which may be used in the acid-hood
are:
sulfuric acid
hydrochloric acid
hydrofluoric acid
Al etchant
BOE 7:1
acetic acid
nitric acid
phosphoric acid
hydrogen peroxide
ammonium hydroxide
The MSDS sheets for these materials can be found in the
yellow MSDS binders in the copier room on the second floor
of Building 39. Users
should become familiar with the appropriate sheet before working with
any of these chemicals.
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Safety: |
Chemicals must be transported to and from
the acid hood Using the chemical cart or single bottle plastic
carrier. Handling chemical
bottles, beakers, or any other vessel must always be done with dry-gloved
hands.
The chemicals used in the acid-hood are all dangerous if you get in contact
with them. They are not carcinogens. HF acid is very dangerous
and HF burns are particularly hazardous. An insidious aspect of HF burns
is that there may not be any discomfort until long after
exposure. These burns are extremely serious and may result in tissue
damage. If you contact HF, flush the area well and be sure to work
under and around your finger nails. Finger nails and cuticles are the
classic areas where people receive burns, having washed off the HF
without washing under their nails. If washed off within a few minutes
of exposure, HF may do no harm. Remember, HF may not produce any
burning sensation until after it has already done damage. All HF burns
should be looked at by a physician.
Acid protective gear MUST be worn when working at this sink. An acid-proof
apron, sleeve guards, acid-proof gloves (atop the normal
clean room gloves), and an acid face mask (with the face shield DOWN)
worn over safety glasses, are all required. ALWAYS know the location
of the nearest eye wash and safety shower. In the case of chemical exposure,
call for help to the person nearest
you and tell them to call the ERT(dial 100). While you are speaking to
the person nearest you, get to the nearest shower or eyewash as fast
as possible. Exposure of the eyes requires flushing with water for at
least 15 minutes. As a precaution, all exposures to the eye will
require a visit to an emergency room for a check up. Contact a staff
member as soon as possible for assistance or call 100. Exposure of the
skin requires immediate removal of all contaminated clothing. Rinse under
the shower for 15 minutes. Contact a staff member as soon as
possible for assistance or call 100.
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Procedure: |
NOTE: Operation will be demonstrated Using
the "Piranha" cleaning process.
- Check Equipment Reservations in CORAL to insure that
you reservedthe correct machine in the correct facility
for the correct date. Another user may have reservations;
it is your responsibility to honor them, if this is the
case.
- Use the "Engage" command in CORAL for
the equipment that you are about to use; use this command
BEFORE you start the operation. Insure that the correct
facility is set (TRL) and that your lot name is entered
correctly.
- Gown up with apron, face shield, arm protectors and rubber
gloves. Surgical gloves and clean room suits do not provide
protection
against corrosive and hazardous chemicals.
- Get chemicals from the chemical "pass-through" and
use the cart to transport them to the acid-hood.
Note: Use the small amounts of chemicals left in the bottles by previous
users before proceeding to open the new bottle.
- Place wafers in the appropriately marked teflon wafer
carrier; use the correct teflon handle for the process
you are about to perform.
- Place wafers in the piranha carrier inside the piranha
sink.
- Add hydrogen peroxide to where the TOP HANDLE bends or
curves.
Note: Steps 8 and 9 will yield the correct H2SO4:H2O2 of 3:1.
- Add sulfuric acid just enough to cover the wafers.
- Remove carrier/wafers from acid mixture and place wafers
inside the DI cascade for 2 minutes with a timer.
- Wash and dry gloved hand(s) used to remove wafer carrier
to avoid dragging chemical to other areas.
- Place a polypropylene glove over the acid glove and
remove the wafer carrier from the cascade (A poly glove
over the acid glove
avoids droping any acidic/other contamination from the glove onto your
clean wafers).
- Change TOP HANDLE for a SIDE HANDLE. Dry wafers in the
SPIN DRYER. (140 sec rinse, 240 sec dry)
- Remove wafers from carrier and return carrier/holder
to its proper shelf.
- Aspirate acids from the sink in the acid hood.
- Rinse the sink at least 3 times.
- Rinse the tip of the aspirator with DI Water and put
it away.
- Inspect bottles for chemical drips and wash if necessary.
- Rinse counter with DI water from the water gun.
- Return all chemicals to the "pass-through".
- Wash and dry acid gloves.
- Remove safety attire and place it in its proper location.
- "DISENGAGE" in CORAL.
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