Characterization of Transformer Coupled Oxygen Plasmas by Trace Rare Gases-Optical Emission Spectroscopy and Langmuir Probe Analysis

Oxygen-containing plasma are used to deposit SiO sub 2 and to etch recently developed organic, low dielectric constant (low-k) materials. Characterization of high-density O sub 2 plasmas is mainly lacking but is nonetheless needed to understand process characteristics such as etched profile evolution, and plasma-induced damage. We have applied Langmuir probe analysis, as well as two techniques developed in this laboratory; trace rare gases-optical emission spectroscopy (TRG-OES) and advanced optical emission actinometry, to measure the electron temperature, T sub e, and the degree of feed-gas dissociation in a high-density, transformer-coupled (TCP) 10 mTorr oxygen plasma. Between 120 and 1040 W input power, the discharge operates in an inductive mode, and T sub e increases from 2.7 to 3.4 eV for the low energy electrons sampled by the Langmuir probe and from ~ 3.5 to 6.0 eV for the high energy electrons sensed by TRG-OES.