A global (volume averaged) model of a Cl2/Ar discharge: I. Continuous power

Abstract

A global (volume averaged) model is applied to a low pressure (1–100 mTorr) high density chlorine discharge diluted with argon. The model is found to be in fair agreement with measurements reported in the literature. Atomic chlorine is the dominating chlorine species at low pressures and low argon content, but with increasing pressure the discharge becomes less dissociated. As the argon content is increased the chlorine dissociation fraction increases and the decrease with pressure becomes less pronounced. The electronegativity was found to decrease proportionally to the argon dilution for a wide range of discharge conditions. The pressure dependence of the Cl+/n+ fraction was found to vary with argon content, from peaking at low pressures in a pure chlorine discharge to peaking at high pressures in an argon dominated discharge. The electron temperature increases with argon content at low and intermediate pressures but decreases at high pressures. Argon–chlorine reactions generally have only a small effect on the creation or destruction of chlorine particles, even at high argon content, except for the loss of Cl− which is rapidly neutralized by Ar+ ions in an argon dominated discharge. Surface losses are most important for positive ion loss at low pressures and become increasingly important when the chamber is made larger or argon is added to the discharge. Volume losses always dominate the loss of neutral Cl atoms at low pressures, but at moderate to high pressures as well when the chamber is either large or small. Argon dilution benefits the neutral surface losses in small chambers but the volume losses in large chambers.