| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThP |
| Session: | Plasma Science Poster Session |
| Presenter: | Z. Chen, University of Houston |
| Authors: | Z. Chen, University of Houston V.M. Donnelly, University of Houston D.J. Economou, University of Houston L. Chen, Tokyo Electron America, Inc. M. Funk, Tokyo Electron America, Inc. R. Sundararajan, Tokyo Electron America, Inc. |
| Correspondent: | Click to Email |
Oxygen-containing plasmas are widely used for etching of fine features in microelectronics manufacturing. Dual-frequency capacitively-coupled reactors offer some advantages over inductive plasmas. The determination of the neutral species density and electron temperature (Te) as a function of radio frequency (RF) power(s) and pressure are important in the understanding and optimization of the plasma etching processes in these systems. In this study, trace rare gases–optical emission spectroscopy (TRG–OES) was used to measure Te, in a dual frequency capacitively-coupled oxygen plasma sustained by a high frequency (60 MHz) “source” upper electrode, and a 13.56 MHz voltage applied to the wafer-supporting lower electrode. TRG-OES is a nonintrusive method for determining plasma electron temperature and, under some conditions, electron energy distributions. The method is based on a comparison of atomic emission intensities from trace amounts of rare gases (a mixture of He, Ne, Ar, Kr, and Xe) added to the plasma, with intensities calculated from a model. In the present experiments, a small amount (5%) of a mixture containing 40% Ne, 20% Ar, 20% Kr and 20% Xe was added to the O2 feed gas. Te was measured across the plasma at a height of 5 mm above the lower electrode as a function of pressure (2-200 mTorr) at different applied RF powers. Oxygen atom densities were estimated by O-atom optical emission (844.6 nm), and rare gas actinometry (Ar, 750.4 nm). Results illustrated that Te in an O2 plasma with 1000 W upper power and no lower electrode power varies inversely with pressure, from 6.8 eV at 2 mTorr to 3.5 eV at 200 mTorr. As power was increasingly applied to the lower electrode, Te at low pressure (e.g. 2 mTorr) hardly changed while, at higher pressures, Te increased to the point that at 500 W lower electrode power, Te was nearly independent of pressure. Percent dissociations derived from O-atom densities were quite low (<5%), even at the highest upper electrode power.