Chlorine dissociation fraction in an inductively coupled plasma measured by ultraviolet absorption spectroscopy

Abstract

Broadband ultraviolet absorption spectroscopy of the weak Cl2 continuum between 250 and 400 nm was used to measure the molecular Cl2 density in pure chlorine inductively coupled plasmas at pressures of 15–100 mTorr and radio-frequency (rf) power up to 800 W. The depletion of the Cl2 density was greatest at high-rf power and low pressure, and reached 80% at 15 mTorr 800 W. A simple global model was developed to explain the variation of the Cl2 dissociation rate as a function of source power and total gas pressure, and was in excellent agreement with the observations.