| Etchants for common microfabrication materials |
| Material to be etched |
Wet etchants |
Plasma etchants |
| Aluminium (Al) |
80% phosphoric acid (H3PO4) + 5% acetic acid + 5% nitric acid (HNO3) + 10% water (H2O) at 35–45 °C |
Cl2, CCl4, SiCl4, BCl3 |
| Indium tin oxide [ITO] (In2O3:SnO2) |
Hydrochloric acid (HCl) + nitric acid (HNO3) + water (H2O) (1:0.1:1) at 40 °C |
|
| Chromium (Cr) |
• "Chrome etch": ceric ammonium nitrate ((NH4)2Ce(NO3)6) + nitric acid (HNO3)
• Hydrochloric acid (HCl) |
|
| Gold (Au) |
Aqua regia |
|
| Molybdenum (Mo) |
|
CF4 |
| Organic residues and photoresist |
Piranha etch: sulfuric acid (H2SO4) + hydrogen peroxide (H2O2) |
O2 (ashing) |
| Platinum (Pt) |
Aqua regia |
|
| Silicon (Si) |
Nitric acid (HNO3) + hydrofluoric acid (HF) |
• CF4, SF6, NF3
• Cl2, CCl2F2 |
| Silicon dioxide (SiO2) |
• Hydrofluoric acid (HF)
• Buffered oxide etch [BOE]: ammonium fluoride (NH4F) and hydrofluoric acid (HF) |
CF4, SF6, NF3 |
| Silicon nitride (Si3N4) |
• 85% Phosphoric acid (H3PO4) at 180°C(Requires SiO2 etch mask)
• Hydrofluoric acid (HF) |
CF4, SF6, NF3 |
| Tantalum (Ta) |
|
CF4 |
| Titanium (Ti) |
Hydrofluoric acid (HF) |
BCl3 |
| Titanium nitride (TiN) |
• Nitric acid (HNO3) + hydrofluoric acid (HF)
• SC1 |
|
| Tungsten (W) |
• Nitric acid (HNO3) + hydrofluoric acid (HF)
• Hydrogen Peroxide (H2O2) |
• CF4
• SF6 |
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