Electron Density Oscillations in CC-RF Oxygen Plasma Investigated by Gaussian Beam Microwave Interferometry
Gaussian beam microwave interferometry (160 GHz, beam waist of 5 mm) is applied to study the electron density in capacitively coupled radio-frequency (RF) oxygen plasma. The microwave interferometry provides immediately the line-integrated electron density without model assumptions. In the considered range of RF power and total pressure, the investigations have shown that the oxygen plasma is dominated by electron density oscillations due to the attachment-induced ionization instability. The frequency of the mostly nonharmonic oscillations ranges between 0.3 and 3 kHz with peak-to-peak line-integrated electron density variations up to 3.5 × 1015 m-2.
Lighthouse Plasma Instability in a Capacitive RF Discharge
Instabilities in an asymmetric capacitively coupled radio frequency argon discharge occur within the pressure range of 70-100 Pa while adding low amounts of CF4. The development of these instabilities is highly dynamic in time and space. The instabilities strongly influence the optical plasma emission and electron density, respectively.
Charged Species Dynamics in an Inductively Coupled Ar/SF6 Plasma
The chemistry of high-density SF6 plasma discharges is not well characterized. In this article, a combination of computational modeling and experimental diagnostics has been utilized to understand charged species dynamics in an inductively coupled Ar/SF6 plasma discharge. The model is based on the two-dimensional Hybrid Plasma Equipment Model with a detailed plasma chemical mechanism for Ar/SF6. In the experiments, absolute electron density and total negative ion density have been measured using microwave interferometry and laser photodetachment, respectively. In addition, we have also utilized prior measurements of mass and energy resolved ion fluxes by Goyette et al. [J. Vac. Sci. Technol. A 19, 1294 (2001)]. Computational results show that all SFx+(x=0–5) ions are present in the plasma discharge. Important negative ions include SF6−, SF5−, and F−. Electron and positive ion densities increase with coil power due to enhanced ionization. However, negative ion densities decrease with coil power as the main...