Etchant-unsaturated species model

Etchant-U maturated Species Model. In the etchant-unsaturated species model described by equations 20-23 (93), specific chemical species derived from electron collisions with etchant gases are considered. 

Gases such as CF4 and SF6 offer advantages because of their low toxicity however, the formation of unsaturated species such as CjF and S F in the discharge can scavenge free F atoms and, in extreme cases, can lead to significant polymer or residue formation. The role of oxygen in these plasmas is twofold. First, in accord with the etchant-unsaturated species model, O atoms react with unsaturated species to enhance F atom generation and to... 

---