Mass-resolved ion energy distributions in continuous dual mode microwave/radio frequency plasmas in argon and nitrogen

Abstract

The control of plasma-surface interactions in terms of synergistic effects of ions, photons, and chemically active species is important for the optimization of plasma enhanced chemical vapor deposition of thin films and for plasma-induced surface modification. In the present work, we use a dual-mode microwave/radio frequency (MW/rf) plasma system, in which we investigate the effect of plasma parameters (gas type and pressure, self-bias voltage, for example) on the energy and flux of ionic species arriving at the specimen surface. We determine the ion energy distribution functions (IEDFs) using a mass spectrometer/energy analyzer, in Ar and N2 discharges, excited at different frequencies. The results for Ar+, N2+, and N+ ions show structured IEDFs at the rf-powered electrode in the single- and dual-frequency modes, while a single peak is observed in the continuous MW plasma. The MW/rf plasma presents substantially higher ion flux and plasma density, and a much thinner sheath than the rf case. Changes in plasma impedance, measured by a rf current–voltage probe, support the results on plasma density and sheath thickness, determined from the IEDFs. The MW/rf discharge impedance displays a resistive behavior in contrast to rf plasma, where the impedance is capacitive.

Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H2

“…Some examples are: Heim and Stori [63], Hallil et al [64], Gans et al [65], Babkina et al [61], and Schiesko et al [32]. In general, one expects the average energies of the ions in the discharge source to be a few eV as determined by the ambipolar field generated by the electrons.…”

A Detailed Investigation of Radicals and Ions in ECR Methane/Argon Microwave Discharge

“…Therefore, it is necessary to investigate the plasma properties in a low‐pressure microwave discharge (such as ECR) in combination with r.f. bias to ensure these conditions . A suitable experimental method fulfilling this requirement is the mass spectrometry of neutral molecules and radicals, so‐called Neutral Mass Spectrometry (NMS), and also the Energy‐Resolved Mass Spectrometry (ERMS) .…”

“…On the contrary, ERMS allows determining of other parameters important for the deposition of DLC films: the composition of the ion flux and its energy. Using mass spectrometry of the methane discharge in ECR/RF, some authors investigated various processes of the formation and changes of the plasma discharge and the distribution of the ionic energy in methane/argon and methane/nitrogen mixtures . The mobility of ions in the methane/argon discharge has been also investigated…”

Analysis of Dual Frequency Confined Capacitively Coupled Plasma at Low Power

“…Hallil et al [5] proposed an investigation on the study of a dual-mode microwave/radio frequency plasma system. They reported that Ar + , N 2 + and N 1 + ions show structured Ion Electron Distribution Functions (IEDF) at the rf-powered electrode.…”