MTL Fabrication

Acid-hood2 - Standard Operating Procedure

CORAL Name: acid-hood2
Model Number: --
Location: TRL
What it does: General-purpose chemical hood that is used for the processing of acids/bases (6.152J, Silicon and Quartz Processing)

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.


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.



NOTE: Operation will be demonstrated Using the "Piranha" cleaning process.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Place wafers in the appropriately marked teflon wafer carrier; use the correct teflon handle for the process you are about to perform.

  6. Place wafers in the piranha carrier inside the piranha sink.

  7. 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.

  8. Add sulfuric acid just enough to cover the wafers.

  9. Remove carrier/wafers from acid mixture and place wafers inside the DI cascade for 2 minutes with a timer.

  10. Wash and dry gloved hand(s) used to remove wafer carrier to avoid dragging chemical to other areas.

  11. 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).

  12. Change TOP HANDLE for a SIDE HANDLE. Dry wafers in the SPIN DRYER. (140 sec rinse, 240 sec dry)

  13. Remove wafers from carrier and return carrier/holder to its proper shelf.

  14. Aspirate acids from the sink in the acid hood.

  15. Rinse the sink at least 3 times.

  16. Rinse the tip of the aspirator with DI Water and put it away.

  17. Inspect bottles for chemical drips and wash if necessary.

  18. Rinse counter with DI water from the water gun.

  19. Return all chemicals to the "pass-through".

  20. Wash and dry acid gloves.

  21. Remove safety attire and place it in its proper location.

Author: Kurt Broderick, 2/00