Use of Piranha Solution-Environmental Health & Safety - Carnegie Mellon University

Monday, June 1, 2015

Use of Piranha Solution

What is it?  Piranha solutions are used to remove organic residues from substrates, particularly in micro-fabrications labs.  The traditional piranha solution is a 3:1 mixture of sulfuric acid and 30% hydrogen peroxide (Do Not Use H202 above 50%).  There is also a base solution, which uses a mixture of ammonium hydroxide with hydrogen peroxide.  The solution may be mixed before application or directly applied to the material, applying the sulfuric acid first, followed by the peroxide.  Piranha solutions are extremely energetic and may result in explosion or skin burns if not handled with extreme caution.  

What to wear?  Protective equipment should include: a full face shield, heavy duty rubber gloves (regular Nitrile gloves will NOT provide sufficient protection), as well as an acid apron to wear on top of the lab coat.

How to handle?  Mix and use in a fume hood or on a ventilated bench.  Always use glass, preferably Pyrex.  Piranha solution is very energetic and potentially explosive.  It is very likely to become hot, more than 100 degrees C.  Handle with care!  Only mix the least amount needed for immediate use.  Do Not Store Piranha!  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.

How to dispose?  Leave the hot piranha solution in an open container until cool, this may take 12 hours.  It is your responsibility to make sure that the open container is very clearly labeled and left in a safe area (fume hood or ventilated bench) for overnight cool down.  Do not collect for disposal.  After the material has cooled, aspirate excess piranha and dispose via the drain, flushing the drain with copious amounts of water.

Further Information:  Please check out the Piranha Solution Fact Sheet, available at:  http://www.cmu.edu/ehs/fact-sheets/piranha-solution-handling.pdf