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Tetramethylammonium hydroxide

CAS Number
75-59-2
EC Number
N/A
Chemical Formula
C4H12N.HO
Molecular Weight
91.15 g/mol

Description

Tetramethylammonium hydroxide ( CAS 75-59-2 ), commonly abbreviated as TMAH, is a quaternary ammonium base used across semiconductor manufacturing, pharmaceutical synthesis, and analytical chemistry. It functions as a strong, metal-free alkali, making it the preferred choice where inorganic base contamination is unacceptable. In semiconductor and flat-panel display manufacturing, it is the standard developer. TMAH is used for photoresist stripping and patterning, where its metal-free profile prevents ionic contamination of wafer surfaces. Pharmaceutical and biotech manufacturers use it as a catalyst and pH-adjusting agent. It is ideal for synthesis steps that require a clean base without introducing sodium or potassium ions. In analytical laboratories, it is used as a quaternizing agent for GC sample preparation. This enables direct injection of fatty acid and biological samples. It also supports etching of silicon wafers in MEMS fabrication, where precise anisotropic etch rates are critical to device geometry. TMAH is supplied as aqueous solution, most commonly at 25% concentration, with lower concentrations such as 5% and 10% available for specific process requirements. Pentahydrate solid form is also available. Electronic-grade and reagent-grade specifications are the primary market grades. Electronic-grade material is held to strict metal impurity limits suited for semiconductor process environments. Contact us for supply of Tetramethylammonium hydroxide Request Quote

Other Names (Synonyms)

Methanaminium, N,N,N-trimethyl-, hydroxide (1:1) | Ammonium, tetramethyl-, hydroxide | Methanaminium, N,N,N-trimethyl-, hydroxide | NMD 3 | TMAH

Key Technical Features

  • High Purity Grade standard
  • Consistent Batch Quality
  • Full Regulatory & REACH Support
  • Global Logistics Network enabled

Physical Properties

Melting Point63 °C
Boiling Point110 °C
Density0.866 g/mL at 25 °C
Flash Point80 °F
Appearancecolourless to yellow liquid
ColorAPHA: ≤10
Odorstrong ammonia-like odor
FormSolution
Water SolubilitySoluble in water.
Vapor Pressure17.5 mm Hg ( 20 °C)
Refractive Indexn 20/D 1.384
pH>13 (H2O, 20°C)

Safety & Handling

Hazard Statements

H300Fatal if swallowed
H301Toxic if swallowed
H310Fatal in contact with skin
H311Toxic in contact with skin
H314Causes severe skin burns and eye damage
H318Causes serious eye damage
H370Causes damage to organs
H372Causes damage to organs through prolonged or repeated exposure
H411(81.2%): Toxic to aquatic life with long lasting effects H300+
H310(36%): Fatal if swallowed or in contact with skin

Trade & Regulatory

HS Code29239000
UN Number3286
ADR Class3
Packing GroupII
Storage Class3 - Flammable liquids
WGK (Germany)1