Tetramethylammonium Hydroxide (TMAH 25%)
CAS Number: 75-59-2
Tetramethylammonium hydroxide (TMAH, 25% aqueous) is a metal-ion-free alkaline etchant that anisotropically etches silicon along crystal planes, providing high selectivity between {100} and {111} planes. It is widely used in MEMS micromachining for fabricating membranes, cantilevers, and microstructures. As a CMOS-compatible alternative to KOH, TMAH introduces no alkali metal contamination.
Technical Specifications
| appearance | Colorless clear liquid |
| purity (%) | ≥25.0 (TMAH assay) |
| Si etch rate (80°C) | ≈ 0.5–1.0 µm/min |
| {100}/{111} selectivity | >30:1 |
| metallic impurities (Na, K, etc.) | ≤1 ppb each |
Applications
- Anisotropic silicon bulk micromachining (MEMS)
- Silicon membrane and diaphragm fabrication
- Positive photoresist development (2.38% dilute)
- V-groove and pyramid structure etching
- CMOS-compatible silicon wet etching
Key Features
- Metal-ion-free chemistry fully compatible with CMOS fabrication
- High {100}/{111} selectivity enabling precise microstructure definition
- Dual-use: both bulk silicon etchant and photoresist developer
- Available at multiple concentrations (2.38%, 5%, 10%, 25%)
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CAS Number
75-59-2
Category
Semiconductor Etching ChemicalsAvailability
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