Hydrofluoric acid: Characteristics
Why chip-grade HF counts metals in parts per trillion
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Commercial HF is sold by strength and impurity level. AHF must be at least 99.9% HF with low water, arsenic and sulphur compounds. Electronic grades need metals at parts per trillion. Aqueous grades of 40-70% suit pickling and glass etching.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Purity (AHF) | at least 99.9% HF; water under about 0.05% (indicative) | Water corrodes steel and harms fluorination yields | Industry specifications (indicative) |
| Arsenic | typically under about 10-20 ppm in AHF; far lower in electronic grade (indicative) | Arsenic poisons catalysts and contaminates downstream products | Indicative |
| Boiling point | 19.5 C | Handled as a refrigerated or pressurised liquid | Physical data |
| Electronic grade metals | parts per trillion per metal (SEMI grades) (indicative) | Defect-free wafer processing | Indicative |
Commercial grades
- Anhydrous HF (AHF) for fluorochemicals
- Aqueous HF 40-70% for pickling and glass
- Electronic grade (SEMI) for wafers
- Buffered oxide etch mixtures