The Relation Between Etch Rate and Optical Emission Intensity in Plasma Etching

The etch rate and the optical emission intensity in the Si etching by a plasma were measured to investigate the relation of the emission intensity to the plasma species concentration. The etch rate as a function of the F emission intensity was obtained by varying the area of loading silicon wafers and the gas flow rate, which seem to have little effect on the electron temperature. The experimental results show that the F emission intensity is linearly proportional to the Si etch rate in the high intensity region, but proportional to the second or larger power of the F emission intensity in the low intensity region. We have proposed two etching models to explain this result. They are based on (i) the competitive mechanism between F atoms and molecules on the silicon surface and (ii) the etching simulation through use of the surface lifetime of F atoms. Finally, we formed continuous equations for generation and dissipation of F and species. From these equations we found that the generation rate of F was kept constant when the load area is varied, and that the disappearances of F and are caused by recombination reactions and exhaustion, respectively.