AVS 62nd International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS+AP+SE-ThA

Paper PS+AP+SE-ThA8
Optical Emission Spectroscopy to Determine Plasma Parameters in an Oxygen Inductively Coupled Plasma

Thursday, October 22, 2015, 4:40 pm, Room 210B

Session: Advanced Ion Implantation and Plasma Doping
Presenter: Nathaniel Ly, University of Wisconsin - Madison
Authors: N. Ly, University of Wisconsin - Madison
J. Boffard, University of Wisconsin - Madison
C.C. Lin, University of Wisconsin - Madison
A.E. Wendt, University of Wisconsin - Madison
S. Radovanov, Applied Materials, Inc.
H. Persing, Applied Materials, Inc.
A. Likhanskii, Applied Materials, Inc.
Correspondent: Click to Email
The success of ion implantation to precisely modify substrate properties requires control of the incident ion energies to achieve the desired depth of the implanted ions. Oxygen plasmas generally contain both O+ and O2+ positive ions, and in plasma immersion ion implantation (PIII) of oxygen, the two will produce different concentration depth profiles due to their different energy/mass ratios. Predicting the overall profile thus requires knowledge of the relative fluxes of the two ion species. Motivated by the long term goal of a robust predictive model, here we combine experiment and numerical simulation to investigate the feasibility of using non-invasive optical emission spectroscopy (OES) to monitor plasma parameters in an oxygen inductively-coupled plasma. Initial experiments made use of a small admixture of argon with the oxygen to take advantage of established techniques involving argon OES. In addition to recording argon emissions, measurements of multiple O, O2, O +, and O2+ emission intensities were made as a function of pressure (1-30 mTorr) and power (500-2000 W). An emission model makes use of available electron impact excitation cross sections for argon and atomic and molecular oxygen to relate measured emission spectra to corresponding plasma parameters, including electron temperature and the dissociation fraction of the neutral oxygen. Data taken while as a function of the percentage of argon in the Ar/O2 mixture showed that even a very small admixture of argon significantly affected the oxygen plasma properties, and more recent experiments have thus focused on oxygen OES in a pure oxygen plasma. The CRTRS 2D/3D plasma code self-consistently and semi-implicitly solves for ICP power deposition and uses Poisson's equation to solve for the electrostatic potential and dynamics of electrons and ions in the drift-diffusion approximation (or full momentum equations). The code also solves for the electron temperature, and generation and quenching of excited states as well as their dynamics. The experimental results are used in combination with simulation predictions to understand the dependence of plasma parameters, including the relative fluxes of O+ and O2+, on the operating parameters.

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The authors acknowledge support from NSF grant PHY-1068670.