Time-resolved measurements of Cl2 density in high-density plasmas and application
Résumé
Absorption at 355 nm, with a pulsed frequency tripled yttrium-aluminum-garnet laser as light source, is used to monitor the time evolution of the Cl2 density in high-density inductively coupled plasmas. The detection limit over a 0.1 s acquisition time is about 0.2 mTorr of Cl2. This technique is well suited for monitoring chlorine density when studying elementary processes in Cl2 containing plasmas. Furthermore, it can be applied to control the process drift in industrial etch reactors resulting from the modification of the chamber walls conditions: by measuring the Cl2 density in a reference Cl2 plasma before etching a wafer, it can be determined if the chamber wall conditions are kept identical from one wafer to another.
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