Time-resolved measurements of Cl_2 density in high-density plasmas and application

摘要

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 Cl_2 density in high-density inductively coupled plasmas. The detection limit over a 0.1 s acquisition time is about 0.2 mTorr of Cl_2. This technique is well suited for monitoring chlorine density when studying elementary processes in Cl_2 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 Cl_2 density in a reference Cl_2 plasma before etching a wafer, it can be determined if the chamber wall conditions are kept identical from one wafer to another.