Phosphoric Acid Semiconductor Grade (H3PO4 85%)
CAS Number: 7664-38-2
Semiconductor grade phosphoric acid (85%) is the standard wet etchant for silicon nitride (Si3N4) with high selectivity over silicon dioxide and silicon. When heated to 160–180°C, it selectively etches Si3N4 at rates of 50–100 Å/min, making it essential for STI and LOCOS process integration. Ultra-pure quality minimizes particle and metal contamination.
Technical Specifications
| appearance | Colorless viscous liquid |
| purity (%) | ≥85.0 (H3PO4 assay) |
| sulfate (SO4) | ≤0.5 ppm |
| chloride (Cl-) | ≤0.1 ppm |
| metallic impurities | ≤1 ppb each |
Applications
- Silicon nitride (Si3N4) hot phosphoric acid etch
- STI (shallow trench isolation) nitride removal
- LOCOS field oxide process nitride strip
- Metal aluminum wet etching (dilute H3PO4/HNO3/HAc mix)
- Phosphate glass (PSG/BPSG) etching
Key Features
- High selectivity for Si3N4 over SiO2 (>30:1) at 160°C bath
- Stable etch rate with controlled water content management
- Ultra-low metallic impurities prevent gate dielectric degradation
- Compatible with hot phosphoric acid recirculating etch tools
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CAS Number
7664-38-2
Category
Semiconductor Etching ChemicalsAvailability
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