Standard Operation Procedure for Piranha Cleaning
Purpose: to remove organic material from sample (acidic solution)
Location: general purpose fumehood or CMOS cleaning station
Chemicals: sulfuric acid, hydrogen peroxide and DI water
Supplies Needed: 2 glass or Pyrex dishes, beakers or graduated cylinders, hotplate, tweezers, texwipes, nitrogen gun, chemical warning labels and PPE
Setup Procedures:
1. Find an available fumehood that is not currently being used for a solvent process. Make sure that the area is free of incompatible chemicals.
2. Fill out the chemical warning label (located at the fumehood) with proper warning information (chemicals, contact information, process time and hazards).
3. Please notify research users that you are going to be using heated acid.
4. Using bottle carries, bring a bottle of sulfuric acid and a bottle of hydrogen peroxide to the fumehood.
5. Setup the hotplate and set the temperature to 120ºC, piranha solution dish, and put on your PPE gear.
6. Measure a precise amount of sulfuric acid into the piranha solution dish that is just enough to cover your sample.
7. Use the 4:1 (H2SO4 : H2O2) ratio to determine the amount of H2O2 to measure in a beaker or graduated cylinder.
8. Slowly pour the hydrogen peroxide into the piranha solution dish. The reaction begins immediately and produces large amounts of heat.
9. Place the piranha solution dish on the hotplate.
10. Let the solution come to temperature (10-15 min).
11. Prepare a DI rinse container while you wait. Fill out another chemical warning label. Triple rinse a glass or Pyrex dish with DI water, then fill the dish with DI water. Set the dish off to the side.
Number of substrates: 1
Process Procedures:
1. Using metal or peek tweezers, carefully place your sample into the piranha solution.
2. Return the chemical bottles to the chemical chase.
3. After 10-20 minutes, remove your sample from the piranha solution and place it into the container of DI water.
4. Take the piranha solution dish off the hotplate and allow it to cool. Turn off the hotplate.
5. Rinse your sample under running DI water (30 seconds).
6. Place your sample on a texwipe and blow dry with the nitrogen gun. Use a sweeping motion while working from one side of the sample to opposite side (1 min).
7. Once the piranha solution is cool (approximately 2-3 hours), while wearing PPE gear, carefully pour it down the sink with plenty of running city water.
8. Rinse the piranha solution container.
Time: approximately 45 minutes + cool down time
Comments:
a. Do not use plastic tweezers or tweezers with a plastic or rubber coating as the piranha will dissolve it.
b. Be sure to rinse your tweezers immediately after transferring your sample in and out of solution.