Kinetics in Etching Processes Density and Flux of Neutral Etchants

Discharge Kinetics in Etching Processes Density and Flux of Neutral Etchants 

To estimate the concentration and fltrx of neutral etchant to the strrface in the discharge described in the previotts sectiort, cortsider as an example the dissociation of oxygen e + O2 - O + O + e. It corresponds, in partictrlar, to the ion energy-driven carbon etching with oxygen considered in Section 8.2.7. The rate coefficient of the dissociation stimrrlated by direct electron impact, A diss(Te), depends on electron temperature and can be expressed in Arrhenitts form as 

The ratio diss/f is about 0.3-0.5 therefore, the direct dependence of the dissociation rate coefficient on electron temperature is not significant. Assuming that atom formation is due to the dissociation of molecules and atom losses are due to vacuum pumping with speed Sp (the loading effect is discussed next), the kinetic balance equation for atomic oxygen density o can be presented as 

In the steady-state conditions dno /dt = 0), the O-atom density in the etching discharge 

Taking into account (8-26), (8-29), and (8-35), the atomic oxygen density can be 

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