Plasma Etching

In dry plasma etching, highly reactive radical ions, generated as a low-pressure plasma from halogen gases, are used to etch fine structures into a substrate wafer. Compounds of fluorine, chlorine and bromine are typically used as the primary etch gases, depending on the material to be structured.

Issues critical to the abatement of plasma etch processes include: loss of production time due to clogging of Metal Etch exhaust lines; corrosion of ducting by aggressive etch – especially bromine – chemistries; the global warming potential of PFC gases; emissions of toxic etch by-products to air and water (e.g. arsenic from GaAs etching).

Plasma Etch Process	Typical Gases Used
Metal Etch	Cl2, BCl3, HCl, CF4, SF6
Polysilicon Etch	Cl2, HBr, SF6, CF4, NF3, C4F8
Dielectric Etch	CF4, CHF3, C2F6, C3F8, C4F8, CH2F2, NF3
Tungsten Etchback	SF6
III-V (GaAs) Etch	Cl2, BCl3, HBr, SF6, CH4