The consequences of plasma chemistry on the uniformity of neutral and ion temperatures in inductively coupled plasmas

Summary form only given. The transport properties of ions and neutrals in radio frequency (RF) inductively coupled plasma (ICP) reactors are important with respect to the resulting surface properties during materials processing. As these transport properties are driven by pressure gradients, the magnitude and uniformity of neutral and ion temperatures are also ultimately important to materials properties. To quantify the processes that control heavy particle heating, a 3-dimensional multi-fluid model has been developed and applied to the investigation of multi-component gases in ICPs. The model is a 3-dimensional hybrid simulator in which electromagnetics, electron energy transport and fluid modules are either serially iterated or run simultaneously on a parallel computer. Separate continuity, momentum and energy equations are solved for each heavy particle species. At the low pressures of interest (< 10s mTorr) momentum slip can occur between species, thereby allowing for different species to have different temperatures. Investigations were performed for ICPs in molecular gas mixtures such as Ar/N/sub 2/, Ar/Cl/sub 2/ and fluorocarbon gases. Ions are primarily heated while accelerating in the electrostatic presheath. The ions then transfer some of this translational energy to neutrals through elastic and charge exchange collisions, raising the neutral gas temperature well above ambient. The effect of inductively coupled power, gas pressure, and flow rate on heavy particle temperatures will be quantified. Consequences of side gas injection and asymmetric pumping on plasma properties will be also be investigated. We found that asymmetric gas injection and pumping produces asymmetries in gas temperatures and densities due to disparities in residence times. These asymmetries produce non-uniformities in the conductivity, thereby producing asymmetric power deposition even if the inductive electric fields are initially symmetric. These asymmetries then feed back to the temperature profiles. This positive feedback is exacerbated by the translational energy released during dissociative excitation of molecular gases. This form of heating also produces temperature disparities between fragments and their parent molecules.