International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 97–104
DOI: 10.46882/2026/IJP/000201
Research Article
Title: Plasma Chemistry and E-to-H Mode Transitions in low-Pressure Chlorine Inductively Coupled Discharges
Names of Authors: P. L. Becker¹, M. G. Nielsen², F. E. Silva³
Authors’ Affiliations:
¹ Institute for Plasma Research, University of Stuttgart, Stuttgart, Germany
² Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
³ Department of Applied Physics, University of São Paulo, São Paulo, Brazil
Abstract: Inductively coupled plasma (ICP) sources are widely used in semiconductor manufacturing for precision etching and thin-film deposition. This study characterises the fundamental plasma parameters of a low-pressure chlorine discharge in an ICP system driven at 13.56 MHz. Experimental measurements were collected using a spatially resolvable, compensated Langmuir probe and automated optical emission spectroscopy (OES). We systematically varied the radio-frequency (RF) power from 50.0 W to 600.0 W and maintained the working gas pressure within a range of 0.5 Pa to 10.0 Pa. The Langmuir probe data revealed a distinct transition from the capacitive mode (E-mode) to the inductive mode (H-mode) occurring at an RF threshold power of approximately 180.0 W at 2.0 Pa. In the H-mode, the electron density increased rapidly by over an order of magnitude, shifting from 3.5 x 10⁹ to 5.8 x 10¹⁰ cm⁻³. Concurrently, the electron temperature dropped slightly from 4.8 eV to 3.2 eV due to enhanced electron-neutral collision rates. Spatially resolved profiles demonstrated optimal radial plasma uniformity within ±3.5% across a 200.0 mm diameter substrate holder under a gas pressure of 1.5 Pa. OES line-intensity ratios validated the electron temperature measurements and confirmed a reduction in the plasma sheath potential from 28.0 V to 14.5 V during the E-to-H mode transition. These experimental measurements provide critical validation data for fluid and particle-in-cell simulations of industrial plasma processing systems.
Keywords: Inductively coupled plasma; Langmuir probe; Optical emission spectroscopy; Electron density; E-H transition; Plasma etching
Manuscript Timeline: Received: June 02, 2026 / Revised: July 05, 2026 / Accepted: July 25, 2026 / Published: August 14, 2026
Citation: Becker, P. L., Nielsen, M. G., & Silva, F. E. (2026). Plasma Chemistry and E-to-H Mode Transitions in low-Pressure Chlorine Inductively Coupled Discharges. International Journal of Physics, 17(8), 97–104.
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