The applicability of actinometry for measuring the absolute concentration of O, N and F atoms in discharge plasma was studied. For this purpose, concentrations of these atoms were measured downstream of an ICP plasma by means of the actinometry method and of appearance potential mass-spectrometry (APMS). Comparison of the results showed good agreement between the two methods. Since the excitation cross sections of electron states O(3p 3P) and O(3p 5P) applied in actinometry are well tested, this allows using the APMS method for absolute calibration of the theoretical excitation cross sections for N and F atoms. As a result, total excitation cross sections of the atomic levels N(3p 4Po), F(3p 2Po) and F(3p 4Do) have been obtained for the first time. Since different types of electron energy distribution function (EEDF) were observed (Maxwellian, bi-Maxwellian and Druyvesteyn) the influence of these possible EEDF types on actinometric coefficients (X  =  O, N, F), that link the ratio of the atom and actinometer intensities with that of their concentrations [X]/[Ar], was also analyzed. It was shown that at the same ionization rate (effective electron temperature) the excitation rate constants are highly sensitive to the shape of EEDF, whereas actinometric coefficients depend on it only slightly. Dependence of actinometric coefficients on electron temperature is positive if the emitting level of the X-atom is lower than that of the actinometer, and negative if vice versa. The energy difference between the emitting states of O and Ar atoms is maximal (~3 eV), so that is not constant for a whole range of electron temperatures typical for discharge plasmas (~2–8 eV). For nitrogen atoms varies considerably with Te only when Te  <  4 eV. In the case of fluorine atoms the energy difference of emitting F and Ar states is only ~1 eV and coefficient is nearly constant in a wide region of Te  >  1.5 eV.

N2 dissociation in pure nitrogen plasma has a long history of research. It seems to be a complex process which comprises many reactions involving various electronic and vibrational nitrogen states whose contributions can vary depending on conditions. In this paper, we studied N2 dissociation in the stationary N2 discharge both experimentally and theoretically. We used a DC glow discharge in a quartz tube in pure N2 at moderate pressures (5–50 Torr). The degree of dissociation, atomic nitrogen loss rate and gas temperature were measured by applying optical emission spectroscopy (OES) and as a result an ‘effective’ rate constant for nitrogen dissociation was obtained across a wide range of the reduced field E/N. The analysis of N2 dissociation was carried out using a specially developed 1D radial self-consistent model which takes into account the spatial inhomogeneities of species concentrations, E/N, electron energy distribution function, Tgas etc, together with fairly complete plasma-chemical kinetics and all the cross-sections known to date for electron kinetics. The model was successfully validated through the experimental results obtained for electric field, gas temperature and N atom density. Comprehensive analysis of closely coupled processes in nitrogen plasmas—gas heating, VDF formation and N2 dissociation—was carried out. Simulations reproduced the experimental data on well and allowed us to evaluate the different contributions of the various dissociation channels considered. It was shown that the nitrogen dissociation mechanism in the stationary N2 discharge is provided by direct electron impact via the excitation of the pre-dissociative states from the vibrationally excited nitrogen molecules N2(X, υ). The upper limit for the rate constant of the processes N2(A)  +  N2(14  ⩽  υ  ⩽  19)  →  N  +  N  +  N2 was estimated to be 5 · 10−14 cm3 s−1.

Low-pressure RF plasma in fluorohydrocarbon gas mixtures is widely used inmodern microelectronics, e.g. in theetching of materials with a low dielectric constant (low-k) materials). The multifold experimental and theoretical study of a radio frequency capacitively coupled plasma at 81 MHz in Ar/CF 4 /CHF 3 has been carried out at 50 mTorr and 150 mTorr gas pressures. Awide set of experimental diagnostics together withhybrid PIC MC model calculations wereapplied to adetailed study of the plasmas. Measurements of the F atoms, HF molecules and CF x radicals, electron density, electronegativity and positive ion composition were performed. Absolutely calibrated VUV spectrometry was carried out to measure the VUV photon fluence towards the electrode. This combined experimental and model approach allowed us to establish the fundamental mechanisms of the charged and neutral species elementary reactions. Dissociative charge transfer reactions and fluoride transfer reactions influencethe main ion (CF 3 + , CHF 2 + ) composition in Ar/CF 4 /CHF 3 plasmaa lot. The mechanisms of heavy ionformation in Ar/CHF 3 are also discussed. The important role of additional attachment mechanisms (besides dissociative attachment to the feedstock gases, CF 4 , CHF 3 ) was analyzed.The catalytic chain mechanism, including the HF molecules, whichdefines theCF x kinetics in Ar/CHF 3 plasma, was validated. This multifold approach enabled us to determine the complicated plasma chemical composition of the active species as well asthe fluxes of VUV photons atthe surface of the processed material, and is aresult thatisimportant for understandinglow-kdamage.

Spectra in the vacuum-ultra violet range (VUV, 30 nm-200 nm) as well as in the ultraviolet(UV) and visible ranges (UV+vis, 200 nm-800 nm) were measured from Ar/CF 3 I and Ar/CF 4 discharges. The discharges were generated in an industrial 300 mm capacitively coupled plasma source with 27 MHz radio-frequency power. It was seen that the measured spectra were strongly modified. This is mainly due to absorption, especially by CF 3 I, and Ar self-trapping along the line of sight, towards the detector and in the plasma itself. The estimated unabsorbed VUV spectra were revealed from the spectra of mixtures with low fluorocarbon gas content by means of normalization with unabsorbed I * emission, at 206 nm, and CF 2 * band ( 1 B 1 (0,v′,0) 1 →A 1 (0,v″,0)) emission between 230 nm and 430 nm. Absolute fluences of UV CF 2 * emission were derived using hybrid 1-dimensional (1D) particle-in-cell (PIC) Monte-Carlo (MC) model calculations. Absolute calibration of the VUV emission was performed using these calculated values from the model, which has never been done previously for real etch conditions in an industrial chamber. It was seen that the argon resonant lines play a significant role in the VUV spectra. These lines are dominant in the case of etching recipes close to the standard ones. The restored unabsorbed spectra confirm that replacement of conventional CF 4 etchant gas with CF 3 I in low-k etching recipes leads to an increase in the overall VUV emission intensity. However, emission from Ar exhibited the most intense peaks. Damage to low-k SiCOH glasses by the estimated VUV was calculated for blanket samples with pristine k-value of 2.2. The calculations were then compared with Fourier transform infrared (FTIR) data for samples exposed to the similar experimental conditions in the same reactor. It was shown that Ar emission plays the most significant role in VUV-induced damage.