Optical Computer Aided Tomography Measurements of Plasma Uniformity in an Inductively Coupled Discharge

Published

July 1, 1998

Author(s)

Eric C. Benck, J R. Roberts

Abstract

Optical computer aided tomography (CAT) is being investigated as a potential in situ diagnostic for measuring plasma uniformity without making assumptions concerning the plasma symmetry. The presence of an opaque vacuum chamber wall severely limits the different directions from which optical emission measurements can be made of the plasma. The tomographic inversion problem with restricted optical access is being solved using Tikhonov regularization. The accuracy of this inversion process is investigated for sevral different observation geometries using theoretical test data generated from known distributions. Optical CAT is applied to an ICP-GEC plasma source, with all the measuremnts made through a single large 152 mm diameter window. Axially asymmetric plasma distributions are demonstrated as a function of gas flowrate and gas composition.

Citation

Characterization and Metrology for ULSI Technology Conference

Pub Type

Journals

Keywords

indictively coupled plasma, optical emissions, plasma uniformity, tomography

Citation

Benck, E. and Roberts, J. (1998), Optical Computer Aided Tomography Measurements of Plasma Uniformity in an Inductively Coupled Discharge, Characterization and Metrology for ULSI Technology Conference (Accessed October 16, 2025)