Etching (microfabrication) - Common Etch Processes Used in Microfabrication

Common Etch Processes Used in Microfabrication

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 (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)

Gallium Arsenide (GaAs)
  • Hydrochloric Acid (HCl)
  • Citric Acid diluted (C6H8O7 : H2O, 1 : 1 ) + Hydrogen Peroxide (H2O2)+ Water (H2O)
  • Cl2, CCl4, SiCl4, BCl3, CCl2F2
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)
  • Potassium hydroxide (KOH)
  • Ethylenediamine pyrocatechol (EDP)
  • Tetramethylammonium hydroxide (TMAH)
  • CF4, SF6, NF3
  • Cl2, CCl2F2
Silicon dioxide (SiO2)
  • Hydrofluoric acid (HF)
  • Buffered oxide etch : ammonium fluoride (NH4F) and hydrofluoric acid (HF)
 CF4, SF6, NF3
Silicon nitride (Si3N4)
  • 85% Phosphoric acid (H3PO4) at 180 °C (Requires SiO2 etch mask)
 CF4, SF6, NF3, CHF3
Tantalum (Ta) CF4
Titanium (Ti) Hydrofluoric acid (HF) BCl3
Titanium nitride (TiN)
  • Nitric acid (HNO3) + hydrofluoric acid (HF)
  • SC1
  • Buffered HF (bHF)
Tungsten (W)
  • Nitric acid (HNO3) + hydrofluoric acid (HF)
  • Hydrogen Peroxide (H2O2)
  • CF4
  • SF6

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