Plasma Diagnostics for Unraveling Process Chemistry

Abstract

This review focuses on the use of diagnostic tools to examine plasma processing chemistry, primarily plasma species energetics, dynamics, and molecule-surface reactions. We describe the use of optical diagnostic tools, mass spectrometry, and Langmuir probes in measuring species densities, rotational and kinetic energies, and plasma-surface reactions. Molecule-surface interactions for MX(n) species (M = C, Si, N; X = H, F, Cl) are presented and interpreted with respect to the molecule's electronic configuration and dipole moments.

Time resolved studies on pulsed fluorocarbon plasmas using chirped quantum cascade lasers

“…Although these complimentary measurements cannot directly be compared with the QCLAS results, they provide a means to assess the trends found in the time resolved experiments. Other stable compounds than the precursor molecule CF 4 , namely C 2 F 6 , C 3 F 8 , CHF 3 and HF, were identified in the spectra (CHF 3 and HF are not displayed in figure 8). A linear fit to the calibration spectra yielded the expected distribution of the perfluoroalkanes: n(CF 4 ) > n(C 2 F 6 ) > n(C 3 F 8 ) [9].…”

“…No other stable molecules than C 3 F 8 may interfere with CF 4 absorption features in the considered range. Potential contributions of CF 3 and CF radicals (figure 3, lower panel) are negligible due to their weak absorption features or low concentrations. Highly resolved QCLAS spectra of pure CF 4 and C 3 F 8 measured in the discharge vessel (without plasma) are displayed in the lower panel of figure 4.…”

“…Thus time resolved information on absolute number densities of transient and stable species is desirable. Several plasma diagnostic methods have been used so far to measure densities of radicals or other neutral species in fluorocarbon containing plasmas [3], among them optical emission spectroscopy [4,5], mass spectrometry [5,6], laser induced fluorescence [6][7][8] or absorption spectroscopy (AS) in the ultraviolet [6,9,10] or infrared (IR) spectral range. Apart from Fourier transform (FT-) IR studies [11,12], tuneable diode laser absorption spectroscopy (TDLAS) has been established as a suitable diagnostic tool for monitoring absolute ground state number densities in plasmas.…”

Cold plasma chemistry and diagnostics

“…The methods most commonly employed rely on mass spectrometry, spectroscopy in different electromagnetic regions and electrical probes [1][2][3]7,28]. Some techniques are suitable to study many different species, but lack the sensitivity to detect the minor ones;…”

Determination of internal temperatures within nitric oxide inductively coupled plasmas

“…[31,33,34] There are several shortcomings of LIF; it is confined to species that possess a fluorescing excited state, requires expensive instrumentation (laser system), and is limited by non-radiative relaxation processes. [35] Notably, recent studies have demonstrated the utility of broadband absorption spectroscopy (BAS) as an alternate technique for probing ground state plasma species. [26,[36][37][38][39][40] Here, we detail a newly constructed combination OES/BAS system for conducting nearly concurrent investigations of both ground and excited state species within NO-containing ICPs.…”