Diagnostics of low-pressure hydrogen discharge created in a 13.56 MHz RF plasma reactor

TL;DR

This study characterizes the plasma parameters of a 13.56 MHz RF hydrogen discharge across various pressures and powers, revealing differences between CCP and ICP modes in temperature and hydrogen dissociation.

Contribution

It provides detailed measurements of electron energy distribution, gas and vibrational temperatures, and hydrogen atom density in RF hydrogen plasma, highlighting mode-dependent variations.

Findings

Gas temperature is constant in CCP mode but increases with pressure and power in ICP mode.

Hydrogen dissociation degree is higher in ICP mode by a factor of 2.

Hydrogen atom density increases with pressure in both modes.

Abstract

A 13.56 MHz RF discharge in hydrogen was studied within the pressure range of 1-17 10 Pa, and at power range of 400-1000 W. The electron energy distribution function and 18 electron density were measured by a Langmuir probe. The gas temperature was determined by 19 the Fulcher-$\alpha$ system in pure H2, and by the second positive system of nitrogen using N2 as the 20 probing gas. The gas temperature was constant and equal to 450 $\pm$ 50 K in the Capacitively 21 Coupled Plasma mode (CCP), and it was increasing with pressure and power in the Inductively 22 Coupled Plasma mode (ICP). Also the vibrational temperature of ground state of hydrogen 23 molecules was determined to be around 3100 and 2000 $\pm$ 500 K in ICP and CCP mode, 24 respectively. The concentration of atomic hydrogen was determined by means of actinometry, 25 either by using Ar (5 %) as the probing gas, or by using H2 as the actinometer in pure hydrogen 26 (Q1 rotational line of Fulcher-$\alpha$ system) The concentration of hydrogen density was increasing 27 with pressure in both modes, but with a dissociation degree slightly higher in the ICP mode (a 28 factor 2). 29 30 Submitted to Physica Scripta 31