Tetramethylammonium hydroxide

Tetramethylammonium hydroxide (CAS 75-59-2), commonly abbreviated as TMAH, is a quaternary ammonium base.

Where is Tetramethylammonium hydroxide used?

• Semiconductor and flat-panel display manufacturing: standard developer
• Photoresist stripping and patterning, where its metal-free profile prevents ionic contamination of wafer surfaces
• Pharmaceutical and biotech manufacturing: catalyst and pH-adjusting agent
• Analytical laboratories: quaternizing agent for GC sample preparation
• It also supports etching of silicon wafers in MEMS fabrication, where precise anisotropic etch rates are critical to device geometry.

Good to know: It functions as a strong, metal-free alkali, making it suitable where inorganic base contamination is unacceptable. It is used for synthesis steps that require a clean base without introducing sodium or potassium ions.

Commercial specifications

• Aqueous solution, most commonly at 25% concentration
• Lower concentrations such as 5% and 10% available for specific process requirements
• Pentahydrate solid form also available
• Electronic-grade and reagent-grade specifications; electronic-grade held to strict metal impurity limits suited for semiconductor process environments