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Specific Chemical Hazards

Fluorinated Acids

Hydrofluoric acid in the SMFL represents a special danger in that it is a toxic. Death can and has occurred from exposure to hydrofluoric acid. The danger arises from the fluorine ion which reacts with the body's calcium to interfere with the transmission of nervous signals, proper functioning of muscles, and electrochemical imbalance. Concentrated hydrofluoric acid represents the greatest danger of fluorine poisoning, but there are other solutions in the SMFL that also represent a fluorine poisoning hazard.

*[SMFL Chemistry#Hydrofluoric Acid ] is a corrosive that is used extensively in semiconductor processing. Primarily for the etching of silicon dioxide.
*[SMFL Chemistry#Ammonium Fluoride] is also a corrosive that is used in the etching of silicon dioxide. Ammonium Fluoride is the main component of[SMFL Chemistry#Pad Etch].
*[SMFL Chemistry#Buffered Oxide Etch (BOE)] contains both Hydrofluoric Acid and Ammonium Fluoride.
*[SMFL Chemistry#Pad Etch] contains Ammonium Fluoride and is used for etching silicon dioxide deposited over aluminum.
*[SMFL Chemistry#Freckle Etch] contains [SMFL Chemistry#Fluoroboric Acid] and is used for etching silicon nodules remaining after aluminum etch.

*Special precautions are needed for the safe handling of HF, NH4F, BOE, Pad Etch and Freckle Etch. They should all be considered as toxic and should never come in contact with the users skin.
*Immediate treatment is required should this occur.

*See the SMFL Users Manual for a full description of the dangers of HF and it's treatment.
** Medical Information about Hydrofluoric Acid and Buffered Oxide Etch (HF & BOE)
** Paper on HF Fatalities (American Journal of Industrial Medicine)
** Hydrofluoric Acid MSDS
** Buffered Oxide Etch MSDS
** HF Medical Book by Honeywell
** Centers for Disease and Control Information on HF
** Image of severe HF burn and description of treatment - somewhat graphic - has a happy ending==Piranha==

*A solution for removing photoresist / organic residues from surfaces. A mixture of [SMFL Chemistry#Sulfuric Acid] and [SMFL Chemistry#Hydrogen Peroxide] ranging from 1:1 to 4:1. At the SMFL, we only use solutions of 3:1 or 4:1.

*Piranha solutions are very exothermic when mixed, rapidly heating to over 100C in a short period.

*Safety Reminders For Use of Sulfuric Acid/Hydrogen Peroxide Mixtures
**It is difficult to dispose of piranha because the waste continues to react and decompose for a long period of time. This builds up pressure in the waste bottles, causing them to burst.
**Commercially stabilized versions of Piranha are available such as Nanostrip (http//
**Personal protective equipment is always required when working with piranha solutions .
**Whenever handling Piranha, only use glass containers, preferably Pyrex.

**In preparing a Piranha solution, add hydrogen peroxide to the sulfuric acid - slowly!
***Piranha solution is very energetic and potentially explosive. When being made it is very likely to become hot, more than 100 degrees C. Handle with care.
***Substrates should be rinsed and dried before placing them in a piranha bath. Piranhas are used to remove residues of photoresist and acetone, not the compounds themselves.
***Adding any acids or bases to piranha or spraying it with water will accelerate the reaction. This includes some photoresist developers , some of which are strong bases.
***Leave the hot piranha solution in an open container until cool on one of the SMFL wetbenches.
***Do not store piranha. Mix only enough fresh solution for each use. Excess solutions should be disposed via the drain (once cool), followed by flushing with copious amounts of water.
***Mixing hot piranha with organic compounds may cause an a very violent reaction. This includes materials such as acetone, photoresist, isopropyl alcohol, and nylon.

== SMFL Imported Chemical Policy==