TMAH Photoresist Developer

New findings regarding TMAH toxicity

From literature

From Microfabrication Lab Network

Please read from bottom up:

From: On Behalf Of Matthieu Nannini, Dr.
Sent: May-19-11 8:29 AM
Subject: Re: [labnetwork] TMAH

Here's an article relating the tragic event.


From: On Behalf Of Robert M. Hamilton

Sent: May-18-11 4:43 PM

To: Matthieu Nannini, Dr.


Subject: Re: [labnetwork] TMAH vs KOH

Matthieu Nannini,

At the Berkeley NanoLab we support both KOH and TMAH use at a dedicated work process station. We have not had issues with these processes. Having said this, we have added the following caution statement about TMAH exposure to our lab and safety manuals after our Office of Environmental Health & Safety shared data about fatal TMAH exposures in Taiwan:

"TMAH (Tetramethylammonium hydroxide) is widely used as a photoresist developer (2-3%) and for the anisotropic etching of silicon (10-15%). TMAH is a strong base and hazardous by ingestion, inhalation, skin (dermal) exposure and eye contact. In addition to alkalinity-related chemical burn, dermal exposure to TMAH may also result in respiratory failure and/or cardiac arrest. A 2010 study of case reports of Taiwan semiconductor factory injuries linked exposure of 25% TMAH to three cases of heart failure. It is important to treat TMAH skin exposure by flooding the effected area with water for at least 15 minutes and to report all exposures."

More generally, caustic burns (KOH or TMAH) can be worse than acid burns. It is difficult to cleanse the orbit of an eye when exposure occurs and caustic quickly penetrate tissue. While 15 minutes may seem an inordinate amount of time for a topical exposure to a chemical, trauma specialists who we've consulted tell us such long rinses have definite value.


Bob Hamilton

Robert M. Hamilton

Marvel NanoLab

University of CA at Berkeley

Rm 520 Sutardja Dai Hall

Berkeley, CA 94720-1754



Hello Mattieu,

IMHO, from a health perspective, TMAH appears far more dangerous than KOH.  We recently prepared a lab-wide notification concerning TMAH and its known but often overlooked dangers based on skin adsorption as opposed to ingestion as an identified route of exposure.

"Materials Safety Bulletin

September 24, 2010

TMAH: New Hazard Awareness Concerning an Old Chemical Tetramethylammonium hydroxide (TMAH) is widely used in micro- or nanofabrication as an etchant and developer. In MSD, TMAH is typically one of several ingredients in commercial etching/stripping mixtures, although it may also be used as a pure chemical.

While it has long been known to be very toxic if ingested, recent industrial experience indicates that skin exposure may result in serious injury/illness or even death. Since 2007, there have been 3 recorded fatalities from skin exposure to TMAH solutions as dilute as 25%. Two of the recorded fatalities occurred due to heart attack despite immediate decontamination and prompt medical care. Thus skin, exposure to >1% TMAH over a few percent of the body must be treated as a life-threatening event. MSDSs may be out of date and not properly describe this high dermal toxicity.

When handling this material, the minimum set of personal protective equipment includes:

safety goggles (not glasses), disposable nitrile gloves, a buttoned lab coat, leg covering and closed-toe shoes. The disposable gloves may only provide brief protection and must be replaced if they become wetted. More protective gloves are the Stansolv or Tri-Ionic glove models sold by MAPA.

In the event of a splash, contaminated clothing must be removed and the wetted area thoroughly washed with soap and water, using the emergency shower if necessary.

Call 911 and summon emergency medical help.

You should not handle TMAH containing materials when working alone.

Tri-Ionic clean room gloves provide excellent protection from TMAH exposure."


David A. Bunzow

User Facilities Program Manager

The Molecular Foundry

Materials Science Division

Lawrence Berkeley National Laboratory

1 Cyclotron Road        MS 67-3207

Berkeley, CA   94720



On 5/18/2011 9:20 AM, Matthieu Nannini, Dr. wrote:

Dear all,

Having only one base dedicated bench running TMAH @ 85C I have now to make a choice between TMAH and KOH since new researcher are asking for KOH. Maintaining the 2 chemicals requires resources that I don't have.

Process wise, TMAH is better with oxide masks but KOH is better with SiN masks. KOH also etches faster and nicer.

My questions are in terms of safety: could you share your experiences with KOH vs TMAH in terms of ease of use, safety, etc...



Matthieu Nannini

McGill Nanotools Microfab