Diagnostics of a wafer interface of a pulsed two-frequency capacitively coupled plasma for oxide etching by emission selected computerized tomography

We have carried out emission selected computerized tomography time and space measurements of the absolute net production rate of Ar(2P₁) in a pulsed capacitively coupled plasma for SiO₂ etching pulsively sustained at 100 MHz and continuously biased at 500 kHz between electrodes in CF₄/Ar and pure Ar at 25 mTorr. Double-layer formation by excessive negatively charged particles in the interface close to the wafer is experimentally estimated only at the wafer's anodic phases during the off-period of the plasma source as seen by the probed net excitation rate. The successive space and time configuration of the net excitation rate will support a sufficient capability to inject energetic negative ions to the biased wafer having microstructures and to neutralize the inner wall to be etched.