A study is undertaken of the loss kinetics of H and Cl atoms in an inductively coupled plasma (ICP) reactor used for the etching of III-V semiconductor materials. A time-resolved optical emission spectroscopy technique, also referred to as pulsed induced fluorescence (PIF), has been combined with time-resolved microwave hairpin probe measurements of the electron density in a pulsed Cl2/H2-based discharge for this purpose. The surface loss rate of H, kwH, was measured in H2 plasma and was found to lie in the 125–500 s−1 range (γH surface recombination coefficient of ∼0.006–0.023), depending on the reactor walls conditioning. The PIF technique was then evaluated for the derivation of kwCl, and γCl in Cl2-based plasmas. In contrast to H2 plasma, significant variations in the electron density may occur over the millisecond time scale corresponding to Cl2 dissociation at the rising edge of the plasma pulse. By comparing the temporal evolution of the electron density and the Ar-line intensity curves with 10% of Ar added in the discharge, the authors show that a time-resolved actinometry procedure using Ar as an actinometer is valid at low to moderate ICP powers to estimate the Cl loss rate. They measured a Cl loss rate of ∼125–200 s−1 (0.03≤γCl≤0.06) at 150 W ICP power for a reactor state close to etching conditions. The Cl surface loss rate was also estimated for high ICP power (800 W) following the same procedure, giving a value of ∼130–150 s−1 (γCl∼0.04), which is close to that measured at 150 W ICP power.

The quarter wave resonator immersed in a strongly magnetized plasma displays two possible resonances occurring either below or above its resonance frequency in vacuum, fo. This fact was demonstrated in our recent articles [G. S. Gogna and S. K. Karkari, Appl. Phys. Lett. 96, 151503 (2010); S. K. Karkari, G. S. Gogna, D. Boilson, M. M. Turner, and A. Simonin, Contrib. Plasma Phys. 50(9), 903 (2010)], where the experiments were carried out over a limited range of magnetic fields at a constant electron density, ne. In this paper, we present the observation of dual resonances occurring over the frequency scan and find that ne calculated by considering the lower resonance frequency is 25%–30% smaller than that calculated using the upper resonance frequency with respect to fo. At a given magnetic field strength, the resonances tend to shift away from fo as the background density is increased. The lower resonance tends to saturate when its value approaches electron cyclotron frequency, fce. Interpretation of these resonance conditions are revisited by examining the behavior of the resonance frequency response as a function of ne. A qualitative discussion is presented which highlights the practical application of the hairpin resonator for interpreting ne in a strongly magnetized plasma.

The effect due to the electron cyclotron frequency on the microwave resonances of a hairpin probe is investigated in a moderate to strongly magnetized plasma. The magnetic field is independently varied over a wide range from 0.01–0.13 T while maintaining the local plasma density constant. At strong magnetic fields the resonance frequency is found to be lower than that measured in vacuum implying that the relative plasma dielectric permittivity, εp>1. It is proposed that the experiments reported here are consistent with a permittivity model that includes magnetic field.

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This paper investigates the application of a floating hairpin probe for measuring the electron density in magnetized plasma. The magnetic field is systematically varied over a wide range (0.01 -0.15 T) and its influence on the probes resonance frequency is studied. The resonance frequency in plasma displays a negative shift when the electron cyclotron frequency becomes comparable with the resonance frequency in vacuum. A general formula for calculating the electron number density in magnetized plasma is hence obtained and the formula is experimentally validated. Comparison of the electron density using the improved formula shows very good agreement with the positive ion density measured by a planar Langmuir probe in the Kamaboko-III negative ion source.