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 |
