PRISM Cleanroom

Piranha Solution Standard Operating Procedure

Piranha is highly reactive solution used to remove organic residues and form a chemical layer on silicon substrates in microfabrication labs. In PRISM Cleanroom max allowed concentration of piranha solution is a 3:1 mixture of concentrated (H2SO4) and 30% (H2O2).

1.0 Material Requirements

1.1 Equipment/Tools needed for process

• The Piranha solution must be always handled inside chemical fume hood aimed to work with acid and corrosive substances (Acid Hood). • Piranha must be processed in quartz or glass beakers and never plastic, using stainless steel tweezers (Teflon is also OK). Piranha attacks organics and it will react violently with plastics such us polyethylene and polypropylene tweezers, bottles, and containers. Therefore, the only materials you should use as tools are glass, quartz, stainless steel and Teflon.

1.2 Chemicals

• Use the solution straight out of the bottle from the chemical supplier: o Sulfuric Acid 95-98% (H2SO4) o Hydrogen Peroxide 30 % (H2O2)

1.2.1 Hazards associated with chemicals:

Sulfuric Acid 95 - 98% (H2SO4)

• Causes severe skin burns and eye damage. • May cause respiratory irritation. • May cause cancer if inhaled. • Harmful to aquatic life. • May be corrosive to metals. Hydrogen Peroxide 30 % (H2O2)

• Oxidizer, may intensify fire. • Causes severe skin burns and eye damage. • May cause respiratory irritation. Toxic if inhaled. • May cause genetic defects. • Harmful if swallowed. Causes damage to organs if swallowed. • Toxic to aquatic life.

Piranha is extremely corrosive and causes extreme burns to skin and severe damage to eyes. It reacts violently and explodes if in contact with organics!

1.3 Administrative controls

• Always handle Piranha solutions inside the fume hood. • Implement the buddy system. In the PRISM Cleanroom, SMP and Packaging laboratories, those who transport liquid chemicals to/from chemical cabinets or perform wet chemistry operations at the fume hoods cannot be alone and must have an in-person Safety Buddy present: at least one Staff or other authorized Labmember in the same laboratory level (line of sight or within hearing distance) at all times. • Know the location the emergency shower and eyewash station. • Review safety data sheet (SDS) for Sulfuric Acid and Hydrogen Peroxide. • Use only enough material needed to complete an experiment.

1.4 Protective equipment needed:

• Face shield on top of safety glasses or safety goggles • Acid-resistant apron • MAPA Trionic Orange gloves (made of nitrile, neoprene, and natural rubber); Wear two pairs of disposable nitrile gloves under the MAPA gloves • Closed toe shoes and long pants

2.0 Procedure Mix 3 parts of concentrated sulfuric acid (e.g. 300 ml) and 1 part of 30 % hydrogen peroxide solution (100 ml) in a glass or quartz beaker. Always add slowly H2O2 to H2SO4. The solution will heat up and start to bubble. Place wafer in piranha bath carefully using stainless steel tweezers. When the Piranha clean is complete (usually 10 - 20 min), rinse sample well with DI and blow dry with N2 gun. Allow piranha solution to cool down to room temperature in a labeled, open container within a hood for several hours prior to final disposal. Piranha should NEVER be sealed in a container, since it continues to evolve gases. Wipe up any drips in the area using water soaked Texwipes and dispose in the acid trash.

3.0 Waste Products Allow solution to cool down to room temperature in an open container before disposing of by using aspirator. Solid waste needs to be placed in a container with a lid and “Hazardous Waste, Acid Contaminated Objects” label.

4.0 Accident Procedures 4.1 Exposure 4.1.1 Skin:

• Go under the emergency shower for 15 minutes and in a meantime remove contaminated clothing. Yell for help! Buddy must contact Public Safety so you can get immediate medical attention.

4.1.2 Eyes:

• Using an eyewash station, rinse with copious amounts of water for a minimum of 15 minutes while holding the lids open. Yell for help! Buddy must contact Public Safety so you can get immediate medical attention.

4.1.3 Inhalation: • Remove to fresh air. Seek medical attention immediately.

4.1.4 Ingestion:

• Get immediate medical attention.

4.2 Spill: How do you deal with a spill inside and outside the fume hood? 4.2.1 For small spills that occur inside of a fume hood (a few drops)

• A few drops of Piranha inside the fume hood can be cleaned by using water soaked Texwipes. The contaminated area must be rinsed with water after the spilled chemical is wiped. Use pH paper to determine when spill has been neutralized. Texwipes used in the clean-up process need to be placed in a container for acid/base-contaminated objects.

4.2.2. For bigger spills that occur inside of a fume hood

• Post a restriction on the hood and contact cleanroom staff

4.2.3 For spills that occur outside of a fume hood

• Evacuate the cleanroom! Use cleanroom phone paging system (PS) to alert other labmembers about the spill (press paging system button (PS) on the phone, lift the handset, send a message and hang up the handset). Immediately notify cleanroom staff (or Public Safety if the spill occurs outside of business hours).

5.0 Related Documents https://www.avantorsciences.com/stibo/search/sdsmix000168_us_en.pdf https://www.avantorsciences.com/stibo/search/sdsmix000510_us_en.pdf

Report all accidents to the cleanroom staff ([email protected]). For emergencies call Public Safety (911 form campus phone).