IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Monday Sessions
       Session PS2-MoM

Paper PS2-MoM3
Spatially (z)-Resolved Electron Temperatures and Species Concentrations in Inductively-Coupled Chlorine Plasmas, Measured by Trace-Rare Gases Optical Emission Spectroscopy

Monday, October 29, 2001, 10:20 am, Room 104

Session: Diagnostics I
Presenter: V.M. Donnelly, Agere Systems
Authors: V.M. Donnelly, Agere Systems
M.J. Schabel, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Determining the spatial dependence of charged and neutral species concentrations and energies in inductively coupled plasmas (ICP) is important for understanding basic plasma chemistry and physics, as well as for optimizing the placement of the wafer with respect to the ICP source to maximize properties such as etching rate uniformity, while minimizing charging-induced damage and feature profile anomalies. We have determined the line-integrated electron temperature (T@sub e@) and Cl-atom number density (n@sub Cl@) as a function of the distance (z) from the wafer in a chlorine ICP, using trace rare gases optical emission spectroscopy (TRG-OES). The gap between the wafer and the window adjacent to the flat coil inductive source was fixed at 15 cm. The pressure was 2, 10, or 20 mTorr (95% Cl@sub 2@, 1% ea. of He, Ne, Ar, Kr, Xe) and the inductive mode power was 340 or 900 W. The % n@sub Cl@ (100% = full dissociation of Cl@sub 2@) increased with power and was highest in the region between mid-gap and the ICP window, reaching nearly 100% at 900 W. T@sub e@ measured by TRG-OES, characteristic mostly of the high-energy (>10 eV) part of the electron energy distribution function (EEDF), peaked near the source under all conditions except 2 mTorr and 900 W, where a maximum T@sub e@ of 5.5 eV was observed at mid-gap. The fall-off in T@sub e@ away from the power dissipation region is mainly due to a preferential loss of high-energy electrons, sensed at high T@sub e@ -conditions by a relative reduction in the intensity of higher energy Ar emission. We can explain this by both local and non-local effects: Electrons lose kinetic energy in reaching the higher potential energy regions of lower electron density near the wafer (non-local effect). At higher pressures, the mean free path for inelastic scattering by high-energy electrons becomes comparable to the reactor dimensions, causing the EEDF to be relatively hot at the source and cool at the wafer (local effect).