Time-resolved measurements of Cl2 density in high-density plasmas and application.

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. [ABSTRACT FROM AUTHOR]